P77S 


ENGINEERING 
LIBRARY 


"er    for    IT?--  n   purposes 

ffnil  :tes   l)epa^tr>e>- 

l'floe    of  experiment   stations.    Bulle 
19.  !!•) 


;^1   Fortier 


fornia 
nal 

ty 


THE  LIBRARY 

OF 

THE  UNIVERSITY 
OF  CALIFORNIA 

LOS  ANGELES 


Issued  July  16, 1912. 

U.  S.  DEPARTMENT  OF  AGRICULTURE. 

OFFICE  OF  EXPERIMENT  STATIONS— BULLETIN  249,  PART  U. 

A.    C.    TRUE,    Director. 


THE  STORAGE  OF  WATER  FOR  IRRIGATION  PURPOSES— PART  II. 


TIMBER  DAMS 

AND"" 

ROCK-FILL  DAMS. 


SAMUEL  FORTIER, 

Chief  of  Irrigation  Investigations, 

AND 

F.  L.  BIXBY, 

Irrigation  Engineer. 


WASHINGTON7: 
GOVERNMENT   PRINTING  OFFICE. 


Property  of  H.  B.  BinTdey. 


1439  Issued  July  16, 1912. 

U.  S.  DEPARTMENT  OF  AGRICULTURE. 

OFFICE  OF  EXPERIMENT  STATIONS— BULLETIN  249,  PART  II. 
A.    C.   TRUE,    Director. 


THE  STORAGE  OF  WATER  FOR  IRRIGATION  PURPOSES— PART  II. 


TIMBER  DAMS 

AND 

ROCK-FILL  DAMS. 


SAMUEL  FORTIER, 

Chief  of  Irrigation  Investigations, 
AND 

F.  L.  BIXBY, 

Irrigation  Engineer. 


WASHINGTON: 

GOVERNMENT  PRINTING  OFFICE. 
1912. 


OFFICE  OF  EXPERIMENT  STATIONS. 

A.  C.  TRUE,  Director. 

E.  W.  ALLEN,  Assistant  Director. 

IRRIGATION  INVESTIGATIONS. 

SAMUEL  FORTIER,  chief. 

R.  P.  TEELE,  assistant  chief.1 

IRRIGATION    ENGINEERS    AND    IRRIGATION    MANAGERS. 

A.  P.  STOVER,  irrigation  engineer,  in  charge  of  work  in  western  Oregon. 

C.  B.  TAIT,  irrigation  engineer,  in  charge  of  work  in  southern  California. 

S.  O.  JAYNE,  irrigation  manager,  in  charge  of  work  in  Washington. 

FRANK  ADAMS,  irrigation  manager,  in  charge  of  work  in  California. 

W.  W.  MCLAUGHLIN,  irrigation  engineer,  in  charge  of  work  in  Utah. 

P.  E.  FULLER,  irrigation  engineer,  in  charge  of  work  in  Arizona  and  of  power 
investigations. 

W.  L.  ROCKWELL,  irrigation  manager  in  charge  of  work  in  Texas. 

DON  H.  BARK,  irrigation  engineer,  in  charge  of  work  in  Idaho. 

MILO  B.  WILLIAMS,  irrigation  engineer,  in  charge  of  work  in  humid  sections. 
-  C.  G.  HASKELL,  irrigation  engineer,  in  charge  of  investigations  of  use  of  water 
for  rice  irrigation  in  the  Gulf  States. 

FRED  G.  HARDEN,  scientific  assistant. 

R.  D.  ROBERTSON,  irrigation  engineer,  assistant  to  irrigation  manager  in  Cali- 
fornia. 

J.  W.  LONGSTRETH,  in  charge  of  work  in  Kansas. 

FRED  C.  SCOBEY,  irrigation  engineer,  in  charge  of  work  in  Wyoming. 

S.  T.  HARDING,  irrigation  engineer,  in  charge  of  work  in  Montana  and  North 
Dakota. 

H.  W.  GRUNSKY,  irrigation  engineer,  in  charge  of  work  in  eastern  Oregon. 

F.  W.  STANLEY,  irrigation  engineer,  assistant  in  humid  sections. 

F.  L.  PETERSON,  irrigation  engineer,  in  charge  of  work  in  Nevada. 

COLLABORATORS. 

GORDON  H.  TRUE,  University  of  Nevada. 

W.  B.  GREGORY,  Tulane  University  of  Louisiana,  in  charge  of  investigations  ot 
pumping  plants  and  canal  systems  for  rice  irrigation  in  the  Gulf  States. 

V.  M.  CONE,  Colorado  Agricultural  Experiment  Station,  in  charge  of  work  in 
Colorado. 

F.  L.  BIXBY,  New  Mexico  Agricultural  College,  in  charge  of  work  in  New 
Mexico. 

S.  H.  BECKETT,  University  of  California,  in  charge  of  cooperation  at  Davis,  Cal. 

IRRIGATION    FARMERS. 

JOHN  H.  GORDON,  R.  G.  HEMPHILL,  W.  H.  LAUCK,  R.  E.  MAHONEY,  and  JOHN 
KRALL,  Jr. 

1  On  furlough,  in  charge  of  irrigation  census  of  Bureau  of  Census. 
249,  Pt  II 

(2) 


Ubrary 

rc 


F775 


LETTER  OF  TRANSMITTAL 


U.  S.  DEPARTMENT  or  AGRICULTURE, 

OFFICE  OF   EXPERIMENT   STATIONS, 

Washington,  D.  C.,  February  26, 1912. 

SIR:  I  have  the  honor  to  transmit  herewith  part  2  of  a  report  on 
the  Storage  of  Water  for  Irrigation  Purposes,  prepared  by  Samuel 
Fortier,  chief  of  irrigation  investigations,  and  F.  L.  Bixby,  irriga- 
tion engineer.  This  part  of  the  report  deals  with  the  construction  of 
timber  and  rock-fill  dams;  part  1  taking  up  earth-fill  and  hydraulic- 
fill  dams.  There  have  been  inquiries  from  all  sections  of  the  country 
for  information  of  this  nature.  In  this  report  suggestions  have  been 
made  which  it  is  thought  will  be  helpful  in  leading  farmers,  coop- 
erative companies,  and  others  to  select  sites,  devise  plans,  and  erect 
structures  such  as  are  commonly  used,  avoiding  some  of  the  mistakes 
of  the  past.  About  20  structures  of  a  more  or  less  typical  nature 
have  been  described  and  illustrated  with  the  same  purpose  in  view. 

It  is  recommended  that  the  report  be  published  as  part  2  of  Bulle- 
tin 249  of  this  office. 

Respectfully,  A.  C.  TRUE, 

Director. 
Hon.  JAMES  WILSON, 

Secretary  of  Agriculture. 

249,  Pt  II 

(3) 


546815 


CONTENTS. 

Page. 

Timber  dams 9 

Introduction 9 

Brush  dams 9 

Log  dams 11 

Pile  dams 12 

Log  crib  dams 13 

Their  origin 13 

Big  Dam,  Cal 14 

Middle  Dam,  Cal 15 

Lower  Strawberry  Dam,  Cal 17 

Lyons  Dam,  Cal 18 

Bowman  Dam,  Cal 20 

Lake  Keechelus  Dam,  Wash.  (U.  S.  Reclamation  Service) 20 

Crib  dams  of  framed  timber , 23 

Diversion  dam  of  Bear  River  Canal,  Utah 24 

Dam  of  Barber  Lumber  Co.,  Idaho 25 

Bonanza  Dam,  Colo 26 

Lower  Yellowstone  Dam,  Mont.  (U.  S.  Reclamation  Service) 26 

Madison  River  Power  Co.  's  Dam,  Mont 29 

Dam  on  Schuylkill  River,  near  Plymouth,  Pa 29 

Tebasco  Dam,  Colo 30 

Big  Hole  River  Dam,  Mont 30 

Butte  City  Water  Co.'s  Dam,  Mont 32 

Canyon  Ferry  Dam,  Mont 34 

Rock-fill  dams 37 

Types  and  designs  of  rock-fill  dams 37 

The  Lower  Otay  Dam,  Cal 41 

East  Canyon  Dam,  Utah 45 

Necessity  for  structure  and  choice  of  type 45 

Foundation  and  core  wall 46 

Excavating  and  placing  the  rock •     47 

Outlet  tunnel  and  valves 48 

Wasteway 4$ 

Results  secured 48 

Raising  the  dam 49 

Second  addition 50 

Cost  of  dam 50 

Beneficial  effects  of  enterprise 51 

Milner  Dam,  Idaho 52 

Minidoka  Dam,  Idaho  (U.  S.  Reclamation  Service) 57 

249,  Pt  II 

(5) 


ILLUSTRATIONS. 


PLATES. 

Page. 
PLATE    I.  Fig.  1.— A  brush  dam,  Weber  River,  Utah.     Fig.  2.— A  brush  dam 

on  the  Yellowstone  River 16 

II.  Fig.  1.— Downstream  view  of  Big  Dam,  South  Fork,  Stanislaus 
River,  Cal.,  showing  lake  and  character  of  timber  on  hillsides. 
Fig.  2. — Same,  showing  debris  gathered  at  foot  of  dam 16 

III.  Fig.  1. — Wasteway,  Middle  Dam,  South  Fork,  Stanislaus  River,  Cal. 
Fig.  2. — Planking  on  upstream  face  of  Middle  Dam,  South  Fork, 
Stanislaus  River,  Cal 16 

IV.  Fig.  1.— Lyons  Dam,  South  Fork,  Stanislaus  River,  Cal.     Fig.  2.— 

Lyons  Dam,  another  view 16 

V.  Fig.  1. — Bulkheads  and  crest  of  spillway,  from  upstream  side, 
Lyons  Dam,  Cal.  Fig.  2. — Diversion  dam  and  flume  below  Lyons 
Dam,  showing  main  dam  in  distance _. 32 

VI.  Fig.  1. — Lake  Keechelus  crib  dam  during  construction,  downstream 
view.  Fig.  2.— The  completed  dam,  Lake  Keechelus,  Wash., 

showing  spillway  and  bulkhead 32 

VII.  Fig.  1. — Method  of  constructing  earth-fill  at  end  of  crib  dam,  Canyon 
Ferry  Dam,  Mont.  Fig.  2. — Canyon  Ferry  Dam  before  recon- 
struction   40 

VIII.  Fig.  1.— East  Canyon 'Dam,  Utah,  showing  temporary  spillway. 
Fig.  2. — East  Canyon  Dam,  showing  steel  core  projecting  and  spill- 
way on  left,  August,  1900 40 

FIGURES. 

FIG.    1.  Repairing  a  brush  dam  on  the  Yellowstone  River 10 

2.  Sketch  showing  manner  of  placing  logs  in  typical  log  dam 11 

3.  Portion  of  a  typical  pile  dam  on  a  small  stream 12 

4.  Spillway,  Big  Dam,  South  Fork,  Stanislaus  River,  Cal 15 

5.  Middle  Dam,  South  Fork,  Stanislaus  River,  Cal.,  showing  manner  of 

laying  logs 16 

6.  Abandoned  portion  of  Middle  Dam,  illustrating  the  placing  of  logs  on 

upstream  slope  of  continuous  crib  dams 16 

7.  Debris  gathered  at  Middle  Dam,  Tuolumne  Water  Co.,  Cal 17 

8.  Lower  Strawberry  Dam,  South  Fork,  Stanislaus  River,  Cal 17 

9.  Plan  and  section  of  Lyons  Dam,  South  Fork,  Stanislaus  River,  Cal. .  18 

10.  Inlet  pipes,  Lyons  Dam 19 

11.  Lake  Keechelus  Dam,  Wash.  (U.  S.  Reclamation  Service),  bottom 

timbers  being  placed 21 

12.  Lake  Keechelus  Dam,  apron  and  spillway  under  construction 22 

13.  Section  of  dam  of  Bear  River  Canal,  Utah 24 

14.  Foundation  of  Barber  Lumber  Co.'s  Dam  on  Boise  River,  near  Boise, 

Idaho 25 

249,  Pt  II 

(7) 


8 

Page. 

FIG.  15.  Section  Bonanza  Dam,  Colo 27 

16.  Lower  Yellowstone  Dam  (U.  S.  Reclamation  Service) 28 

17.  Section  of  timber  dam  on  Schuylkill  River,  near  Plymouth,  Pa 29 

18.  Butte  City  Water  Co.'s  crib  dam  for  Reservoir  No.  2,  Basin  Creek, 

Mont 33 

19.  Section  of  Canyon  Ferry  Dam,  Mont.,  as  reconstructed 35 

20.  Canyon  Ferry  Dam,  showing  the  reconstructed  portion  as  well  as  part 

of  old  dam 36 

21.  Section  of  typical  rock-fill  dam 37 

22.  Sketch  showing  method  commonly  used  for  facing  rock-fill  dams  with 

timber 38 

23.  Section  of  concrete  base  with  steel  core  protected  by  asphalt  concrete 

encased  in  wooden  forms 40 

24.  Core  wall  of  Lower  Otay  Dam,  Cal.,  under  construction 43 

25.  Lower  Otay  Dam.     Two  Lidgerwood  cableways  delivering  rock  from 

quarry 44 

26.  Plan,  elevation,  section,  and  details  of  East  Canyon  Dam,  Utah 46 

27.  Plan  and  section  of  Milner  Dam,  Twin  Falls  project,  Snake  River, 

Idaho 52 

28.  General  view  of  Milner  Dam,  Snake  River,  Idaho 53 

29.  Gates  in  Milner  Dam,  Snake  River,  Idaho 54 

30.  Milner  Dam,  showing  lifting  apparatus  operated  by  electric  motor 55 

31.  Headgates,  Twin  Falls  Canal  system,  South  Side,  at  Milner,  Idaho. . .  57 

32.  Minidoka  Dam,  Snake  River,  Idaho  (U.  S.  Reclamation  Service). . . .  58 

33.  Riprapped  slope,  Minidoka  Dam,  Snake  River,  Idaho 59 

34.  Concrete  dam  in  diversion  channel,  Minidoka  project,  Idaho 59 

35.  Upstream  side,  concrete  dam  in  diversion  channel,  Minidoka  project, 

Idaho  (U.  S.  Reclamation  Service) 60 

36.  Spillway,  Minidoka  Dam,  Idaho  (U.  S.  Reclamation  Service) 61 

37.  Plan  and  sections,  Minidoka  Dam,  Idaho,  showing  sequence  of  con- 

struction (U.  S.  Reclamation  Service) , 62 

38.  Showing  derrick  handling  skips,  and  cableways  in  action;  also  show- 

ing double  trestle  from  which  earth  was  dumped  in  the  back-filling, 

Minidoka  project,  Idaho  (U.  S.  Reclamation  Service) 63 

249,  Pt  II 


THE  STORAGE  OF  WATER  FOR  IRRIGATION  PUR- 
POSES-PART II. 


TIMBER  DAMS. 


INTRODUCTION. 

Wherever  the  pioneer  has  made  his  way  to  the  frontier,  the  timber 
dam  in  one  or  more  of  its  many  forms  has  sprung  into  existence. 
The  purposes  for  which  it  is  built  change  with  time  and  place.  The 
old  grist  and  saw  mills  that  dot  the  landscapes  east  of  the  Missis- 
sippi River  are  mute  witnesses  of  the  important  part  timber  dams 
played  in  the  storage  and  diversion  of  water  for  mechanical  purposes 
in  the  early  days  of  the  Republic.  The  need  of  stored  water  for 
hydraulic  mining  in  the  West  more  than  half  a  century  ago  aroused 
new  interest  in  suitable  materials  for  dams,  and  timber  structures 
became  common  in  the  mining  districts.  The  decline  in  hydraulic 
mining  was  followed  by  the  rapid  rise  and  progress  of  irrigation,  so 
that  the  same  dams  which  had  stored  water  for  the  miners  were  sub- 
sequently used  by  the  irrigators.  In  recent  years  the  development 
of  water  power  to  generate  electricity  has  opened  up  still  another 
field  for  such  structures. 

The  timber  dam  will  doubtless  continue  to  be  regarded  as  a  suit- 
able and  economical  structure  in  all  the  smaller  and  less  expensive 
irrigation  systems,  not  only  because  of  its  cheapness  in  first  cost  and 
the  ease  and  rapidity  with  which  it  can  be  constructed,  but  because 
of  its  adaptability  to  a  wide  range  of  conditions  and  locations.  In 
the  following  pages  are  given  the  results  of  studies  of  the  different 
types  of  timber  dams,  varying  from  the  cheap  brush  dam  to  the 
more  costly  framed  crib  dam.  Loose  rock  or  rock-fill  dams  are  then 
taken  up.  Earth-fill  and  hydraulic-fill  dams  are  treated  in  a  sepa- 
rate bulletin.1 

BRUSH  DAMS. 

From  the  earliest  practice  of  irrigation  in  the  arid  region  up  to 
the  present  time,  water  has  been  diverted  from  the  natural  stream  into 
the  irrigators'  ditches  by  means  of  brush  and  rock.  In  the  early 

!U.  S.  Dept.  Agr.,  Office  Expt.   Stas.  Bui.  249,  pt.   1. 

34818°— Bull.  249,  Pt.  II— 12 2 

(9) 


10 

stages  of  irrigation  development  this  practice  was  quite  general. 
The  settlers  had  little  money  of  their  own  to  expend  for  water  sup- 
plies, and  it  was  seldom  that  they  could  borrow  from  outsiders. 
Necessity  compelled  them,  therefore,  to  resort  to  makeshifts.  Brush 
was  abundant  and  accessible,  and  it  required  but  little  labor  when 
the  spring  floods  had  subsided  to  build  a  barrier  in  the  bed  of  a 
stream  sufficiently  high  to  divert  the  water  into  the  headgate  of  a 
ditch.  In  building  these  temporary  barriers  the  pioneers  realized 
that  next  spring's  flood  might  necessitate  repairs  or  wash  them  en- 
tirely away,  but  even  where  heavy  repairs  or  renewals  were  necessary 
each  season,  the  builders  were  amply  repaid  for  the  effort  put  upon 
them. 


FIG.   1.— Repairing 


the  Yellowstone  River. 


From  the  use  of  a  small  mat,  weighted  with  rock,  placed  in  creeks 
and  small  streams,  the  practice  grew  to  include  the  damming  up  of 
some  fairly  large  rivers  for  diversion  purposes.  A  brush  dam  of  the 
old  type  is  shown  in  Plate  I,  figure  1.  For  20  years  or  more  this 
cheap  weir  and  its  predecessors,  that  were  carried  by  floods  into  Great 
Salt  Lake,  served  to  divert  water  from  Weber  Eiver,  Utah,  into  the 
Davis  and  AVeber  Counties  Canal. 

In  the  larger  dams  of  this  kind  the  brush  is  tied  into  bundles  with 
galvanized-iron  wire,  these  bundles  being  deposited  in  layers  with 
the  butts  downstream  and  weighted  with  rock  and  boAvlders.  A 
good  example  of  this  construction  is  shown  in  Plate  I,  figure  2.  This 
dam  has  served  for  a  score  or  more  of  years  to  divert  water  from  the 
Yellowstone  River  into  the  Big  Ditch,  which  irrigates  about  25.000 
acres  of  land  near  Billings,  Mont.  Figure  1  is  a  view  of  the  same 
dam  when  it  was  undergoing  repairs. 

249,  Pt  II 


11 

LOG  DAMS. 

This  type  of  timber  dam  is  practical  only  where  there  is  an  abun- 
dance of  suitable  timber.  Its  use  in  this  country  is  associated  with 
the  building  of  the  old-time  mill  ponds  which  furnished  heads  to 
turn  water  wheels  or  floated  saw  logs.  In  more  recent  times  the 
same  kind  of  structure  has  been  used  extensively  in  the  wooded  por- 
tions of  the  West  in  building  dams  for  the  diversion  and  storage  of 
water  for  irrigation  purposes. 

Whether  used  for  diverting  or  impounding  water  the  crest  of  the 
dam  should  be  made  so  it  can  be  used  as  a  spillway  for  its  entire 
length.  This  can  be  accomplished  by  the  addition  of  flashboards. 
The  logs  are  thus  kept  continuously  wet.  Without  flashboards  the 
upper  timbers  become  dry  in  periods  of  low  water  and  wet  in  periods 
of  high  water,  and  this  alternating  condition  induces  early  decay. 
Log  dams  range  from  5  to  15  feet  in  height  and  are  so  built  that 
heavy  floods  may  pass  over  their  crests  without  injury  to  the  struc- 
tures. Straight-crested  dams  with  wide  aprons  are  the  most  com- 
mon. The  aprons  should  be  sufficiently  wide  to  carry  the  water 
beyond  the  point  where  an  eddy  is  liable  to  form.  A  few  dams 
of  this  type  are 
curved  on  their 
upstream  face,  and 
others  are  built 
with  an  obtuse  an- 
gle. The  timbers 
used  are  generally 

10   to   20    inches   in       FlG-  2- — Sketch  showing  manner  of  placing  logs  in  a  typical  log 

diameter     at     the 

butt  end.  A  sketch  showing  the  position  in  which  the  logs  are 
placed  is  shown  in  figure  2.  First  the  largest  logs  are  placed  side 
by  side  with  their  smaller  ends  upstream  until  the  entire  bed  of 
the  stream  is  covered.  These  logs  constitute  the  foundation  for  the 
dam  proper  and  also  for  the  apron.  Two  or  more  courses  laid 
in  a  similar  position  are  then  added  to  complete  the  apron,  each 
course  being  stepped  upstream  10  to  15  feet.  In  this  manner  a  ter- 
raced apron  is  obtained.  The  dam  proper  is  then  carried  up  in 
courses,  the  logs  being  laid  close  together  parallel  to  the  stream  flow, 
in  such  a  way  that  the  downstream  face  formed  by  the  butt  ends 
of  the  logs  will  be  nearly  vertical.  Binders  3  or  4  inches  in  diameter 
are  placed  across  each  course  of  logs  near  the  downstream  slope  and 
secured  to  the  logs  by  tree  nails  or  spikes,  thus  adding  stiffness  to 
the  structure.  The  spaces  between  the  succeeding  courses  of  logs 
are  filled  with  saplings,  brush,  stone,  and  earth,  in  order  to  make 
the  dam  as  nearly  water-tight  as  possible.  To  complete,  several 
binders  are  placed  on  the  top  course  of  logs,  and  a  filling  of  stone  and 

249,  Pt  II 


12 

earth  is  deposited  on  the  upstream  side  and  finished  to  a  uniform 
slope  of  about  3  to  1.  The  earth  filling  serves  to  secure  water- 
tightness  and  to  prevent  to  a  large  extent  the  passage  of  water 
beneath  the  dam. 

PILE  DAMS. 

The  pile  dam  is  a  modification  of  the  log  dam  and  is  well  adapted 
to  mud  bottoms,  or  to  any  river  bed  which  affords  a  firm  foothold 
for  piling,  provided  a  proper  penetration,  8  or  10  feet,  can  be  obtained. 
Rectangular  cribs  are  first  built,  extending  out  from  the  stream  bank 
on  either  side.  These  are  inclosed  by  piling  on  three  sides  and  filled 
with  rock,  their  height  being  2  or  3  feet  above  that  of  the  finished 
dam.  Between  these  cribs  three  rows  of  10  to  16  inch  piling  are 
driven,  extending  across  the  stream  and  intersecting  the  cribs  some- 
where between  the  center  of  their  ends  and  their  upstream  face. 
The  piles  in  the  two  downstream  rows  are  driven  close  together 
except  where  they  permit  of  an  occasional  longitudinal  log  passing 

between  them,  the 
purpose  of  the  lat- 
ter being  to  tie 
down  the  apron. 
This  is  shown  in 
figure  3,  which  is 
a  sketch  of  a  por- 
tion of  such  a  dam. 
The  upstream  or 
third  row  is  placed 
far  enough  above 

PIG.  3. — Portion  of  a  typical  pile  dam  on  a  small  stream. 

the  two  lower  ones 

to  permit  of  binders  being  placed  between  it  and  the  two  down- 
stream rows  of  piles  across  the  stream.  The  individual  piles  of 
the  upstream  row  are  spaced  far  enough  apart  from  one  another 
to  admit  the  butt  ends  of  logs  between  them.  Logs  30  or  40  feet 
long  are  next  laid  on  the  upstream  side  of  the  piling,  with  their  small 
ends  upstream  and  their  butts  extending  between  the  piling  of  the 
u'pstream  row  and  against  the  piling  of  the  downstream  rows.  When 
a  course  of  these  logs  has  been  put  in  place,  a  binder  is  laid  across 
it  in  the  space  provided  between  the  rows  of  piling.  Other  courses 
of  logs  and  binders  are  placed  in  the  same  manner,  thus  giving  the 
logs  on  the  upstream  side  a  slight  incline  which  increases  with  each 
succeeding  layer  placed.  The  binders,  piles,  and  horizontal  logs  are 
all  thoroughly  driftbolted  to  each  other. 

The  upstream  side  of  the  main  piling  is  chinked  up  with  stones 
that  can  not  wash  through,  and  then  a  filling  of  earth  and  gravel 
is  placed  against  the  dam  and  around  the  logs  on  the  upstream  side 
to  prevent  scouring  beneath  the  piles.  The  dam  is  completed  by  the 
construction  of  an  apron  to  prevent  the  erosive  action  of  the  water 

249,  Pt  II 


13 

on  the  downstream  side.  This  apron  extends  downstream  from  the 
piling  a  distance  at  least  equal  to  the  height  of  the  dam  above 
the  apron  floor.  Its  length  is  also  influenced  by  the  character  of  the 
stream  bottom.  In  the  construction  of  this  apron  a  row  of  sheet 
piling  is  first  driven  to  anchor  the  latter  and  prevent  the  water  from 
undercutting  it.  This  row  of  sheet  piling  is  placed  downstream  from 
the  main  piling  at  a  distance  governed  by  the  length  of  the  apron. 
These  sheet  piles  should  extend  6  or  10  feet  below  the  level  of  the 
apron  floor. 

To  carry  the  apron  two  mud  sills  of  12  to  14  inch  squared  logs  are 
placed,  one  next  to  the  lower  row  of  piles  on  the  downstream  side 
and  the  other  just  below  the  sheet  piling,  which  is  securely  fastened 
thereto.  These  mud  sills  extend  clear  across  the  stream  bed.  If  the 
ground  is  uneven  it  will  have  to  be  built  up,  preferably  with  rocks 
and  gravel,  in  order  to  form  a  support  for  the  apron  sills  and  floor. 
The  apron  floor  is  formed  by  cross  logs  or  heavy  planking  laid  upon 
the  mud  sills  and  fastened  securely  to  them  and  to  the  piling.  A 
structure  of  this  type  can  be  safely  built  from  5  to  20  feet  in  height 
and  forms  a  satisfactory  diversion  or  impounding  dam  or  both. 

LOG  CRIB  LAMS. 

THEIR  ORIGIN. 

The  old  log  crib  dams  built  in  the  early  days  of  mining  in  Cali- 
fornia are  among  the  best  examples  of  their  type  in  existence.  These 
dams  were  originally  constructed  by  water  companies  to  conserve  the 
flood  waters  of  the  streams  on  which  they  were  built  and  to  maintain 
a  uniform  flow  throughout  the  year  for  mining  operations  of  various 
kinds,  chiefly  placer  mining.  With  the  enforcement  of  the  laws  in- 
stituted by  the  Debris  Commission,  placer  mining  was  discontinued 
to  a  great  extent,  and  the  dams  were  neglected  for  a  number  of  years, 
as  the  demand  for  water  for  other  purposes  could  be  easily  supplied 
at  that  time  from  the  natural  stream  flows.  These  dams  are  being 
used  again,  however,  for  a  purpose  entirely  different  from  that  for 
which  they  were  built.  Irrigation  is  now  making  its  urgent  demands 
upon  water  supplies  and  every  means  of  conserving  the  spring  and 
winter  run-off  is  being  planned  and  carried  to  practical  completion. 

During  the  years  1852-1856  the  Tuolumne  Water  Co.,  of  California, 
constructed  three  large  log  crib  dams  and  storage  reservoirs  on  the 
South  Fork  of  the  Stanislaus  River,  the  lower  one  being  34  miles 
northeast  of  Sonora,  Cal.  These  reservoirs  were  for  the  purpose  of 
storing  water  through  the  dry  season.  The  water  was  let  down 
from  one  reservoir  to  another  through  the  regular  channel  of  the 
river.  At  Long  Camp  nearly  all  the  water  was  diverted  into  a  large 
ditch  and  used  for  hydraulic  mining  at  Columbia,  Jamestown,  and 
the  surrounding  country.  In  all  three  dams  the  original  intention 

249,  Pt  II 


14 

was  to  build  them  larger,  but  when  they  were  nearly  finished  a  dis- 
covery of  gold  in  another  district  started  every  one  to  the  new  field, 
leaving  the  dams  unfinished.  They  were  completed  and  made  fit  for 
service,  however,  in  1856.  Brief  descriptions  and  illustrations  of 
these  typical  miner's  dams  follow. 

BIG  DAM,    CAL. 

The  construction  of  Big  Dam  was  the  most  difficult  on  account  of 
its  location.  Plate  II,  figure  1,  gives  a  view  of  the  greater  portion  of 
the  lake  and  the  dam.  A  considerable  portion  of  the  material  was 
packed  in  on  mules,  as  access  to  the  site  was  possible  in  no  other  way. 
Timber  was  scarce  and  small  and  had  to  be  hauled  or  dragged  for  a 
long  distance.  The  trees  in  the  picture  are  growing  in  the  crevices 
of  the  rugged  granite  slopes  and  are  dwarfed  and  unfit  for  use.  The 
dam  is  385  feet  long  and  about  40  feet  high  in  the  highest  place. 
Originally  it  was  62  feet  in  height,  but  through  the  decay  of  the 
timbers  the  top  20  feet  has  disappeared,  the  last  part  being  removed 
in  the  fall  of  1907.  Plate  II,  figure  2,  shows  the  debris  below  the 
dam  and  the  manner  in  which  the  upper  slope  was  strengthened  after 
the  upper  20  feet  had  been  cut  away.  This  upper  part  of  the  dam 
was  situated  where  the  timbers  were  subjected  to  alternate  wetting 
and  drying,  which  in  time  destroyed  the  wood  fiber.  Where  the 
wood  has  been  continuously  wet,  it  is  in  a  fair  state  of  preservation 
after  more  than  50  years  of  service. 

The  foundation  of  the  dam  is  laid  on  the  bare  granite  rock,  the  bot- 
tom timbers  being  laid  lengthwise  of  the  dam  and  bolted  to  the  rock 
every  5  feet  by  steel  rods  1  inch  in  diameter,  for  which  holes  had  been 
drilled.  The  succeeding  layers  of  logs  were  placed  in  the  regular 
crib  fashion,  notched  one  upon  another.  They  were  fastened  together 
by  boring  holes  and  driving  wooden  pins  through  successive  timbers. 
The  manner  of  laying  up  the  timbers  forming  the  cribwork  is  shown 
in  figure  5,  page  16,  a  view  of  the  Middle  Dam.  The  upper  face  of 
Big  Dam  was  built  of  8-inch  logs  laid  on  an  incline  side  by  side  and 
lengthwise  with  the  flow  of  the  stream,  the  spaces  being  chinked  with 
small  wedges  and  earth.  Figure  6,  page  16,  showing  an  abandoned 
portion  of  Middle  Dam,  illustrates  the  manner  of  placing  the  logs. 
These  logs  were  notched  into  the  cribwork,  had  holes  bored  through 
them,  and  were  fastened  down  with  wooden  pins.  This  log  facing,  in 
the  case  of  the  Big  Dam,  became  so  rotted  that  it  was  replaced  in 
1899-1900  by  two  thicknesses  of  2  by  12  inch  planking.  These  were 
lap- jointed,  the  joints  on  the  top  course  being  covered  with  1  by  6 
inch  battens.  The  dam  conserves  in  the  reservoir  a  water  supply  of 
1,890  acre-feet,  which  is  equivalent  to  a  continuous  flow  of  about  45 
cubic  feet  per  second  for  a  period  of  three  weeks.  The  reservoir  has 
a  watershed  of  18  square  miles  and  an  average  annual  precipitation 
of  10  to  15  feet  of  snow. 

249,  Pt  II 


15 

The  surplus  water  from  the  reservoir  flows  over  a  spillway  con- 
structed at  one  end  of  the  dam.  This  spillway  (fig.  4)  is  35  feet 
wide  and  3  feet  below  the  crest  of  the  dam.  It  is  equipped  with 
flashboards,  so  that  the  water  level  of  the  reservoir  may  be  varied  at 
least  2  feet.  The  posts  supporting  the  flashboards  are  6  by  6  inches 
and  spaced  7  feet  centers.  At  times  when  the  river  is  low  the  water 
is  drawn  from  the  reservoir  by  means  of  a  "  slum "  gate,  which  is 
opened  and  closed  by  a  threaded  screw,  at  the  top  of  which  is  a 
capstan  nut  operated  by  an  iron  bar.  The  gate  slides  on  the  upstream 
slope  of  the  dam.  The  dam  is  in  a  bad  state  of  repair,  it  being  diffi- 
cult to  renew  any  part,  owing  to  the  decayed  condition  of  the  wood. 


FIG    4.— Spillway,  Big  Dam,  South  Pork  Stanislaus  Uiver,  Cal. 
MIDDLE   DAM,   CAL. 

This  dam  is  located  10  miles  below  Big  Dam  on  the  same  river. 
Its  structure  is  the  same  as  Big  Dam,  being  of  the  continuous  crib 
type.  (Fig.  5.)  The  dam  was  originally  650  feet  long,  but  about 
300  feet  was  abandoned  and  in  its  place  a  small  earth-fill  dam  was 
constructed.  The  portion  of  the  cribwork  remaining  was  retimbered 
where  it  had  become  rotted  and  two  thicknesses  of  2  by  12  inch 
planking  were  placed  on  the  upper  slope.  (PI.  Ill,  fig.  1.)  The 
abandoned  portion  of  the  dam  and  the  manner  in  which  the  logs 
were  placed  are  shown  in  figure  6.  In  the  fall  of  1907  a  new  apron 
was  placed  in  the  wasteway,  the  old  apron  having  rotted  out.  (PI. 
Ill,  fig.  2.)  The  floor  of  the  apron  was  built  of  4  by  12  inch  planks 
and  the  uprights  are  4  by  6  inch,  against  which  flashboards  are  placed 
to  vary  the  water  level  of  the  lake.  The  manner  of  placing  the  logs 

249,  Pt  II 


16 

in  the  cribs  and  the  notching  of  one  on  another  has  been  shown  in 
figure  6.    The  timber  used  in  the  construction  of  this  dam  Avas  taken 


FIG.  5. — Middle  Dam,  South  Fork  Stanislaus  River,  Cal.,  showing  manner  of  laying  logs. 

from  the  reservoir  site.  The  site  was  not  thoroughly  cleared,  how- 
ever, only  the  best  timber  suitable  for  the  construction  of  the  dam 
being  used.  This  standing  timber  is  rotting  at  the  water's  edge  and 


pIG    6. — Abandoned  portion  of  Middle  Dam,  illustrating  the  placing  of  logs  on  upstream 
slope  of  continuous-crib  dams. 

falling  into  the  lake.  The  current  carries  the  debris  down  to  the  dam, 
forming  a  big  jam  on  the  spillway.  A  boom  of  logs  was  originally 
placed  above  the  dam  to  prevent  this  condition,  but  on  account  of 

249,  Pt  II 


U.  S.  Dept.of  Agr.,  Bui.  249,  Pt.  II,  Office  of  Expt.  Stations.     Irrigation  Investigations.  PLATE   I. 


FIG.  1.— BRUSH  DAM,  WEBER  RIVER,  UTAH. 


FIG.  2.— A  BRUSH  DAM  ON  THE  YELLOWSTONE  RIVER. 


U.  S.  Dept.  of  Agr.,  Bui.  249,  Pt.  II,  Office  of  Expt.  Stations.     Irrigation  Investigations.  PLATE   II. 


FIG.  1.— VIEW  OF  BIG  DAM,  SOUTH  FORK  STANISLAUS  RIVER,  CAL.,  SHOWING  LAKE  AND 
CHARACTER  OF  TIMBER  ON  HILLSIDES. 


FIG.  2.— SAME,  SHOWING  DEBRIS  GATHERED  AT  FOOT  OF  DAM. 


U.  S.  Dept.  of  Agr.,  Bui.  249,  Pt.  II,  Office  of  Expt.  Stations.     Irrigation  Investigations.  PLATE   III. 


FIG.  1.— WASTEWAY,  MIDDLE  DAM,  SOUTH  FORK  STANISLAUS  RIVER,  CAL. 


FIG.  2.— PLANKING  ON  UPSTREAM  FACE  OF  MIDDLE  DAM,  SOUTH  FORK  STANISLAUS 
RIVER,  CAL. 


U.  S.  Dept.  of  Agr.,  Bui.  249 


,  Pt.  I!,  Office  of  Expt.  Stations.     Irrigation  Investigations.  PLATE  IV. 


FIG.  1  .—LYONS  DAM,  SOUTH  FORK  STANISLAUS  RIVER,  CAL. 


FIQ.  2.— LYONS  DAM,  ANOTHER  VIEW. 


17 


improper  connections  between  the  logs  the  boom  broke, 
shows  the  result. 


Figure  7 


7. — Debris  gathered  at  Middle  Dam,  Tuolumne  Water  Co.,  Cal. 
LOWER  STRAWBERRY  DAM,   CAL. 

This  dam  is  the  third  in  the  chain  of  lakes.     It  is  located  about 
2  miles  above  Strawberry  Camp  and  34  miles  from  Sonora,  Cal. 


FIG.  8. — Lower  Strawberry  Dam,  South  Fork  Stanislaus  River,  Cal. 


The  dam  is  320  feet  long  and  35  feet  high  and  is  a  continuous  crib 
constructed  of  logs  notched  one  on  another.     (Fig.  8.)     A  storage 

34818°— Bull.  249,  Pt.  11—12 3 


18 

reservoir  is  formed  by  it  which  has  a  capacity  of  1,183  acre-feet, 
which  is  equivalent  to  a  continuous  flow  of  about  40  cubic  feet  per 
second  for  15  days.  The  spillway  is  104  feet  wide,  with  a  log  apron 
20  feet  wide,  built  of  logs  8  to  10  inches  in  diameter.  The  foundation 
of  the  dam  is  similar  to  that  of  the  two  dams  previously  described, 
and  the  cribwork  is  carried  up  in  the  same  manner. 


PLAN  OF  UPPE«  LA/CH  OF  Loos. 

FIG.  9. — Plan  and  section  of  Lyons  Dam,  South  Fork  Stanislaus  River,  Cal. 
LYONS   DAM,    CAL. 

This  dam  (PL  IV,  figs.  1  and  2)  is  the  fourth  of  the  series  and 
completes  the  chain  of  reservoirs  belonging  to  the  Tuolumne  Water 
Co.  It  was  constructed  in  1896-97,  after  plans  and  specifications 
prepared  by  the  consulting  engineer.  The  contract  called  for  $17,000, 
but  with  extras  the  actual  cost  of  building  was  $21,000.  A  plan  and 
elevation  of  this  dam  are  shown  in  figure  9. 

The  foundation  is  located  in  the  stream  bed  on  solid  granite  rock. 
The  log  cribbing  was  constructed  directly  on  the  rock,  and  where  an 
uneven  surface  was  found,  concrete  was  used  to  give  the  lowest. logs 

249,  Pt  II 


19 

a  proper  bearing.  At  the  upper  toe  of  the  dam  the  concrete  was 
filled  in  on  both  sides  and  flush  with  the  top  of  the  stringer  end 
timber.  The  entire  foundation  was  secured  to  bedrock  with  long 
anchor  bolts,  well  leaded,  in  holes  drilled  for  the  same.  The  crest 
of  the  dam  is  148  feet  between  bulkheads  or  wings.  The  total  length 
of  dam  is  250  feet  and  its  maximum  height  55  feet.  All  logs  for 
the  cribwoik  were  cut  in  the  vicinity  of  the  dam  site  and  average 
10  to  20  inches  in  diameter.  The  upstream  face  of  the  dam  is  built 
on  a  2^  to  1  slope  and  is  covered  with  two  thicknesses  of  4  by  12  inch 
planking  over  the  entire  surface  with  an  additional  3  by  12  inch  layer 
over  the  loAver  half.  The  layers  of  planking  are  separated  by  a 


FIG.  10. — Inlet  pipes,  Lyons  Dam. 

heavy  grade  of  roofing  paper  to  increase  the  imperviousness.  At 
both  ends  of  the  dam  bulkheads  consisting  of  cribbing  were  built 
up  about  7  feet  above  the  crest  of  the  dam  and  well  anchored  to 
the  bedrock.  These  bulkheads  were  then  faced  with  planking  and 
filled  with  loose  rock,  adding  to  the  stability.  (PI.  V.  fig.  1.) 

When  the  flood  season  is  at  its  height,  the  water  over  the  spillway, 
or  that  portion  of  the  crest  between  the  two  bulkheads,  is  sufficient 
to  supply  a  stream  of  about  60  cubic  feet  per  second.  In  the  drier 
season  of  the  year  water  is  drawn  from  the  reservoir  by  means  of  a 
tunnel  cut  through  solid  rock  at  one  end  of  the  dam.  Three  16-inch 
pipes  set  in  concrete,  controlled,  respectively,  by  three  16-inch  gate 
valves,  form  the  outlet  to  the  reservoir.  (Fig.  10.)  The  dam  is 

249,  Pt  II 


20 

also  provided  with  two  sand  gates  on  its  face,  with  openings  2  feet 
by  5  feet  6  inches.  These  are  used  to  sluice  out  silt  from  the  reser- 
voir. Whether  the  water  flows  over  the  crest  of  the  dam  or  is 
drawn  out  through  the  tunnel,  it  passes  down  the  main  channel  of 
the  river  to  a  point  about  1,500  feet  below  the  dam,  where  it  is 
diverted  by  a  small  crib  dam  into  a  flume  2  feet  deep  and  74  feet 
wide.  (PI.  V,  fig.  2.)  The  average  flow  of  water  delivered  into  this 
flume  is  about  45  cubic  feet  per  second,  while  the  maximum  is  about 
55  cubic  feet  per  second.  The  water  is  furnished  to  miners  for  power 
purposes  and  to  farmers  for  the  irrigation  of  fruit  trees  and  garden 

truck. 

BOWMAN  DAM,   CAL. 

This  dam  is  located  on  the  South  Fork  of  the  Yuba  River,  Cal., 
and  is  another  illustration  of  the  types  of  dams  used  in  the  early 
days  of  hydraulic  mining.  The  brief  description  here  given  follows 
that  contained  in  Schuyler's  work  on  reservoirs.1 

It  impounds  the  drainage  from  19  square  miles  of  the  high  Sierras 
and  has  a  maximum  capacity  of  21,070  acre-feet.  The  dam  was 
built  in  1872  to  the  height  of  72  feet.  It  consists  of  a  continuous 
limber  crib  of  unhewn  cedar  and  tamarack  logs,  notched  and  bolted 
together  and  filled  with  loose  rock.  The  upper  and  lower  slopes 
were  1  to  1,  the  upstream  slope  being  faced  with  a  layer  of  pine 
planking  laid  horizontally. 

In  1875  the  dam  was  raised  to  a  height  of  100  feet  by  adding  an 
embankment  of  stone  to  the  lower  slope  wide  enough  to  carry  the 
entire  structure  to  the  desired  height,  including  the  cribwork.  The 
outer  face  of  this  embankment  was  made  as  a  hand-laid  dry  rubble 
wall  in  which  stones  weighing  f  to  4^  tons  each  were  used.  The 
wall  was  made  15  by  18  feet  thick  at  the  base  and  6  to  8  feet  at  the 
top.  Eibs  extending  up  and  down  the  slope  were  bolted  to  the  wall 
on  the  water  face  with  f-inch  rods,  5  feet  long.  A  facing  of  planks 
was  spiked  to  these  ribs.  There  were  three  layers  of  planking,  each 
3  inches  thick,  for  the  bottom  25  feet ;  two  layers,  each  3  inches 
thick,  for  the  next  35  feet;  and  one  layer,  3  inches  thick,  for  the 
remaining  36  feet. 

The  dam  is  425  feet  long  on  top  and  has  a  base  width  of  180  feet. 
Like  many  other  of  the  earlier  types  of  rock-filled  crib  dams,  it  was 
built  with  an  obtuse  angle  in  the  center,  the  apex  pointing  upstream. 
Its  cost  was  $151,521.44. 

LAKE  KEECHELUS  DAM,  WASH. 

[U.  S.  Reclamation  Service.] 

This  dam  is  located  in  the  Cascade  Mountains  in  Washington,  on 
the  Northern  Pacific  Railway,  about  4  miles  north  of  Stampede  Tun- 

*J.  D.  Schuyler.     Reservoirs  for  Irrigation,  Water  Power,  and  Domestic  Water  Supply. 
New  York  and  London,  1908,  2.  ed.,  p.  60. 
249,  Pt  II 


21 

nel,  the  reservoir  formed  thereby  being  part  of  the  storage  system  of 
the  Yakima  project  of  the  United  States  Reclamation  Service.  This 
dam  is  a  temporary  structure  which  impounds  12,000  acre-feet  of 
water.  It  is  to  be  replaced  later  by  a  permanent  clam  which  will 
conserve  98,000  acre-feet.  The  dam  is  about  14  feet  high  in  the 
maximum  section  and  25G  feet  long.  It  was  founded  on  a  gravelly 
bottom  cut  2  feet  below  the  original  stream  bed.  All  loose  material 
was  cleared  from  the  foundation  site  and  leveled  sufficiently  to  give 
a  good  bearing  to  the  bottom  timbers.  The  cribwork  consisted  of 
logs  not  less  than  10  inches  in  diameter  at  the  small  end  and  gained 
at  the  intersection  to  a  vertical  thickness  of  8  inches.  The  logs  were 
notched  one  on  another  and  piled  alternately,  crosswise  and  length- 
wise of  the  dam,  in  cribs  8  feet  square  center  to  center  of  logs.  (Fig. 


FKJ.  11. — Lake  Keechelus  Dam,  Wash.  (U.  S.  Reclamation  Service),  bottom  timbers  being 
placed  showing  gains  cut  in  splicing  logs. 

11.)  At  each  intersection  the  logs  were  secured  to  each  other  by 
drift  bolts  1  inch  in  diameter  and  16  inches  long.  The  upstream 
side  of  the  dam  is  vertical,  while  the  downstream  slope  is  1|  to  1, 
breaking  into  a  6  to  1  slope  near  the  bottom.  At  the  toe  of  the 
upstream  side  a  trench  4  feet  deep  and  2  feet  wide  was  dug  the  full 
length  of  the  dam.  Sheathing  consisting  of  two  courses  of  1|  by 
12  inch  plank  was  laid  with  lap  joints  on  the  vertical  upstream  side 
and  extended  from  the  bottom  of  the  trench  to  the  crest  of  the  dam. 
The  sheathing  was  nailed  to  the  cribbing  by  wire  spikes.  The  inside 
course  had  one  5-inch  wire  spike  and  the  outside  course  two  6-inch 
wire  spikes  at  every  intersection  with  a  horizontal  log.  The  trench 
was  then  filled  with  selected  material,  which  was  thoroughly  puddled, 

249,  Pt  II 


22 

and  a  clay  and  gravel  embankment  with  a  slope  of  2  to  1  was  placed 
on  the  upstream  side  of  the  cribbing.  The  surface  of  this  embank- 
ment was  then  paved  with  hand-placed  riprap.  The  cribbing  on  the 
downstream  side  (PI.  VI,  fig.  1)  was  constructed  so  that  the  logs 
were  on  a  1£  to  1  slope  for  the  upper  12  feet  (horizontal  measure- 
ment), and  then  a  slope  of  6  to  1  for  the  next  12  feet.  The  latter 
slope  breaks  onto  the  apron,  which  is  24  feet  wide.  The  apron  and 
spillway  were  covered  with  6-inch  hewed  timbers  with  1^-inch  open 
joints  and  secured  to  the  logs  at  every  intersection  with  two  f  by  13 
inch  drift  bolts.  (Fig.  12.)  All  holes  for  drift  bolts  were  bored 
-J  inch  smaller  than  the  diameter  of  the  bolt.  To  bring  the  channel 
up  flush  with  the  apron  a  rock  fill  with  a  slope  of  15  to  1  was  placed 
at  the  toe  of  the  apron  and  consisted  of  hand-placed  riprap. 


FIG.  12. — Lake  Keechelus  Dam,  apron  and  spillway  under  construction,  crest  log  in  place 
and  apron  completed  on  east  end. 

The  cribs  for  the  dam  proper  were  filled  with  gravel  and  rock. 
The  cribs  for  the  apron  were  filled  entirely  with  rock,  75  per  cent  of 
which  was  at  least  one-tenth  cubic  foot  in  volume.  The  outlet  con- 
sists of  three  openings  through  the  bulkhead,  each  4  by  6  feet,  inside 
measurements.  The  entrance  to  the  outlet  conduit  is  in  excavation 
with  a  side  slope  of  1^  to  1,  the  bottom  and  sides  being  paved  with 
12  inches  of  hand-placed  riprap.  The  partition  timbers  are  12  by  12 
inches,  hewed,  and  are  secured  to  each  other  by  f  and  20  inch  drift 
bolts  at  intervals  of  5  feet.  Sheet  piling  was  driven  against  the  bulk- 
head around  the  entrance  of  the  conduit  so  as  to  prevent  undermin- 
ing of  the  bulkhead.  This  piling  was  6  by  12  inches,  formed  by 

249,  Pt  II 


23 

2-inch  planks,  tongue  and  groove,  and  had  an  average  penetration  in 
the  soil  of  9  feet.  The  completed  dam  is  seen  in  Plate  VI,  figure  2, 
showing  the  bulkhead  with  the  sheathing  partially  finished.  The 
location  of  the  outlet  is  indicated  in  the  picture  by  two  white  streaks, 
caused  by  the  outrushing  water.  It  is  also  shown  in  figure  12.  The 
conduits  are  roofed  over  by  hewed  timber  laid  transversely  across  par- 
titions and  sides,  the  minimum  thickness  of  these  timbers  being  8  inches. 
The  flow  of  water  from  the  reservoir  is  controlled  by  flashboards 
placed  at  the  upstream  end  of  the  outlet  conduit.  These  flashboards 
are  pieces  of  4  by  6  inch  timber,  6  feet  6  inches  long,  and  have  hooks 
on  each  end  by  which  they  are  lifted. 

CRIB  DAMS  OF  FRAMED  TIMBER. 

In  the  days  when  lumber  was  cheap  and  cement  dear  this  type  of 
dam  was  used  extensively  in  the  West.  When  built  in  the  rocky 
channel  of  a  river  it  served  to  raise  the  water  above  the  intake  of  a 
diversion  canal  and  at  the  same  time  permitted  the  spring  floods  to 
pass  over  its  crest.  Structures  of  this  kind  have  been  used  for  both 
diverting  and  impounding  water,  and  their  use  is  pretty  certain  to  con- 
tinue in  all  timbered  localities  remote  from  transportation  facilities. 

Apart  from  stability,  water  tightness,  and  general  efficiency,  the 
chief  feature  to  consider  is  durability.  No  wooden  structure  will  last 
long  if  it  is  alternately  wet  and  dry.  Since  the  lower  portion  of  a 
dam  of  this  kind  is,  of  necessity,  wet  most  of  the  time,  and  the  upper 
portion  part  of  the  time,  it  should  be  so  designed  that  some  water 
would  flow  over  the  crest  the  year  through.  If  water  in  a  dry 
season  is  too  valuable  to  permit  of  this  waste,  a  set  of  low  flashboards 
should  be  built  on  the  crest  to  keep  the  dam  continuously  wet. 

The  principal  features  of  crib  dams  of  this  type  are  described  and 
illustrated  in  the  examples  which  follow.  As  the  foundation  is  an 
important  part  of  the  construction  of  all  types  of  dams,  and  as  tim- 
ber dams  are  no  exception  to  this  rule,  a  few  brief  descriptions  are 
introduced  at  the  beginning  to  illustrate  the  difficulties  which  are 
encountered  in  the  building  of  such  foundations  in  different  locali- 
ties and  to  suggest  the  methods  employed  for  overcoming  these  diffi- 
culties. Some  of  these  descriptions  are  necessarily  brief,  since  there  is 
much  similarity  in  some  of  the  structures,  and  to  avoid  repetition  only 
such  points  are  mentioned  as  will  best  illustrate  the  one  idea  in  view. 

Much  of  this  matter  is  equally  appropriate  to  the  subject  of  log- 
crib  dams  hitherto  discussed.  The  reader  is  also  referred  to  the  de- 
scription of  the  Lyons  Dam,  page  18,  and  to  that  of  the  Canyon  Ferry 
Dam,  page  34,  as  having  special  points  on  the  subject  of  foundations. 

Following  these  brief  descriptions  which  have  special  reference  to 
foundations,  the  construction  of  some  typical  framed-timber  crib 
dams  is  given  in  greater  detail. 

249,  Pt  II 


24 

DIVERSION  DAM  OF  BEAU  RIVER  CANAL,  UTAH. 

This  structure  was  built  in  1890  at  a  cost  of  $45,000  to  divert 
water  from  Bear  River  into  two  canals,  having  a  depth  of  10  feet, 
and  a  computed  carrying  capacity  of  1.000  cubic  feet  per  second  each. 


Its  length  along  the  crest  is  370  feet,  maximum  height  17£  feet, 
and  base  width  38  feet.  The  upstream  face  has  a  slope  of  2  to  1 
and  the  downstream  face  f  to  1.  Figure  13  represents  a  cross  section 
of  the  dam.  In  laying  the  foundation,  solid  rock  was  found  about 
two-thirds  of  the  distance  across  the  bed,  and  the  mudsills  were 

249,  Pt  II 


25 

securely  anchored  to  bedrock  in  the  manner  shown.  Over  the  balance 
of  the  bed  the  mudsills  were  laid  on  clay,  and  upon  the  completion 
of  the  dam  and  the  rise  of  the  water  in  the  forebay,  it  sprung  a  leak 
through  the  clay  underneath  the  mudsills.  This  leak  was  small  at 
first  but  soon  increased  and  finally  the  whole  river,  carrying  over 
20,000  cubic  feet  per  second,  passed  beneath  the  crib.  The  timber 
crib,  being  anchored  into  the  rock,  remained  intact,  and  when  the 
spring  floods  subsided  a  concrete  wall  4  feet  thick  and  15  feet  high 
was  built  under  the  dam  where  the  foundation  had  washed  out.  This 
wall  rested  upon  bedrock  and  was  tied  into  the  upper  toe  of  the 
dam.  The  balance  of  the  excavation  caused  by  the  escaping  water 
was  filled  with  rock.  For  the  past  20  years  it  has  given  entire  satis- 
faction. Figure  13  shows  the  completed  structure. 

This  partial  failure  directs  special  attention  to  the  strength  of 
such  structures  when  properly  designed  and  built,  and  the  need  of 
some  kind  of  a  cut-off  wall  between  the  foundation  and  some  im- 


FIG.  14. — Foundation  of  Barber  Lumber  Co.'s  Dam  on  Boise  River,  near  Boise,  Idaho. 

pervious  stratum.  Some  60  linear  feet  of  this  dam  was  suspended 
in  the  air  without  foundation  for  at  least  six  months,  with  flood 
water  passing  underneath  and  impinging  against  the  upstream  face. 
There  is  no  question  that  this  failure  might  have  been  averted  by 
inserting  sheet  piling  or  a  framed  bulkhead  at  the  upper  toe  of 
the  dam. 

DAM  OF  BARBER  LUMBER  CO.,   IDAHO. 

This  dam  is  founded  upon  a  soft  sandstone  rock  in  the  bed  of  the 
Boise  Eiver  5  miles  above  Boise,  Idaho,  and  in  order  to  obtain  a  good 
footing  for  the  foundation,  12  by  12  inch  sills  were  placed  in  trenches 
cut  transversely  with  the  stream,  as  shown  in  figure  14.  These  sills 
were  placed  under  the  upstream  edge  of  the  dam  proper  and  under 
the  apron,  which  is  24  feet  wide.  The  sills  at  the  upper  and  lower 
toes  of  the  dam,  respectively,  and  those  under  the  apron  were  bolted 
down  to  bedrock  by  bolts  1|  to  1J  inches  in  diameter  and  4  to  4|  feet 
34818°—  Bull.  249,  Pt.  11—12 4 


26 

long.  Bolts  were  omitted  in  those  sills  immediately  under  the  dam 
proper.  The  cribbing  above  was  secured  to  the  foundation  timbers 
by  drift  bolts  which  are  shown  in  the  figure. 

BONANZA   DAM,   COLO. 

This  dam  is  located  at  Pitkin,  near  Aspen,  Colo.,  on  Castle  Creek. 
In  constructing  the  dam  the  gravel  on  the  foundation  site  was  re- 
moved to  a  depth  of  8  or  9  feet,  or  until  bedrock,  a  red  sandstone, 
was  reached.  Two  trenches  were  then  cut  in  the  sandstone,  trans- 
versely with  the  stream  flow,  one  at  the  upper  toe  and  one  at  the 
lower  toe  of  the  dam.  A  12  by  15  inch  sill  was  placed  in  each  trench 
and  embedded  in  concrete,  allowing  the  tops  of  the  sills  to  come  just 
above  the  surface  of  the  sandstone.  These  sills  were  placed  30  feet 
5  inches  apart,  outside  measurement,  and  formed  the  upper  and  lower 
toes  of  the  dam,  respectively.  The  sills  at  the  upstream  toe  were 
bolted  to  bedrock  by  1-inch  round  anchor  bolts,  3  feet  long  and 
spaced  6  feet  centers.  Eound,  red  spruce  logs  were  placed  longitudi- 
nally with  the  stream  with  their  ends  notched  on  these  sills  and  a 
good  bearing  upon  the  sandstone  bedrock.  These  logs  had  been 
peeled  and  were  18  inches  at  the  small  ends  and  placed  on  30-inch 
centers.  They  were  secured  to  the  sills  by  drift  bolts  f  inch  in 
diameter  and  27  inches  long.  For  the  first  4  feet  above  the  level  of 
the  foundation  the  cross  timbers  forming  the  upper  and  lower  slopes 
of  the  dam  were  the  same  size  as  the  sills — 12  by  15  inches.  At  this 
elevation  the  timbers  on  the  upstream  face  were  bolted  through  to 
bedrock  by  round  anchor  bolts  1  inch  in  diameter,  6  feet  long,  and 
spaced  8  feet  centers.  (Fig.  15.) 

LOWEB  YELLOWSTONE  DAM,  MONT. 

IU.  S.  Reclamation  Service.] 

This  structure  on  the  Lower  Yellowstone  project  of  the  United 
States  Reclamation  Service  is  a  rock-filled,  timber-crib  weir  on  a 
pile  foundation.  It  has  a  height  of  12  feet  and  raises  the  water  about 
5  feet.  The  bed  of  the  Yellowstone  River  at  this  point  consisted  of 
sand  and  gravel,  in  places  firmly  cemented  with  clay,  with  occasional 
detached  fragments  of  ledge  rock.  In  order  to  obtain  a  firm  footing 
without  excessive  excavation,  piles  were  driven  averaging  6  feet  cen- 
ters in  a  line  transversely  with  the  dam  and  8  feet  centers  longitudi- 
nally with  the  dam,  and  were  then  framed  together,  as  shown  in 
figure  16.  These  piles  extended  to  an  average  depth  of  20  feet,  where 
a  stratum  of  tough  blue  clay  was  encountered,  which  gave  an  excel- 
lent bearing.  At  the  upper  and  lower  toes  of  the  dam,  respectively, 
a  row  of  sheet  piling  was  driven  to  an  average  depth  of  15  feet.  The 
piling  used  was  of  sufficient  length  to  project  well  above  the  water 
surface  and  thus  form  a  cofferdam  during  the  construction.  The 

249,  Pt  II 


27 

round  piles  were  first  driven  for  the  entire  length  of  the  dam,  and 
the  cofferdam,  excavation,  and  framing  of  timbers  were  then  done  in 
four  sections,  the  excess  length  of  sheet  piling  being  cut  off  and  the 
cofferdam  wrecked  after  the  completion  of  each  section. 


^     ^  ^-^ffisemm 

•nf.  /?cc/  Sonc/sfone  SectrocK 

ountt  •ynchot-  to/fs 
tff/fj  r-usT. 

FIG.  15. — Section  of  Bonanza  Dam,  Colo. 

The  original  design  called  for  3-ply  sheet  piling  of  the  Wakefield 
type,  the  specifications  being  as  follows: 

Each  sheet  pile  shall  be  formed  of  three  planks  (2  by  12  inch)  of  uniform 
width,  thickness,  and  length.  All  middle  planks  of  these  piles  shall  be  dressed 
on  one  side  to  a  uniform  thickness  and  the  piles  shall  be  formed  with  tongue 
and  groove  and  fastened  with  clinched  steel  wire  spikes.  The  lower  end  of 
each  pile  shall  be  chamfered  and  the  piles  shall  be  driven  in  close  contact  with- 
out shattering.  If  not  in  close  contact,  or  if  shattered,  the  sheet  piles  shall  be 
withdrawn  and  replaced  properly  so  as  to  accomplish  the  required  purpose  of 
preventing  leakage. 
249,  Pt  n 


28 


249,  Pt  II 


29 

It  was  found  that  this  type  could  not  be  driven  satisfactorily  in  the 
material  which  was  encountered,  and  sheet  piles  made  up  of  10  by  10 
inch  sticks,  with  tongue  and  groove  of  3  by  4  inch  pieces  spiked  on 
with  f  by  10  inch  bolt  spikes,  were  substituted.  These  sheet  piles 
proved  very  satisfactory,  both  as  to  driving  and  as  to  the  exclusion  of 
water,  with  the  exception  of  two  sections  on  the  downstream  line  with 
an  aggregate  length  of  236  feet.  At  these  sections  the  underlying 
strata  could  not  be  penetrated  by  the  wooden  sheet  piles,  and  steel 
sheet  piling  was  required. 

MADISON  RIVER  POWER  CO.'S  DAM,   MONT. 

This  structure  is  a  rock-filled,  timber  crib  dam  on  Madison  River, 
14  miles  from  Norris,  Mont.  It  has  a  length  of  183  feet,  maximum 
height  of  34  feet,  and  a  base  width  of  92  feet.  It  is  an  overflow  dam 
with  vertical  upstream  slope  and  stepped  on  the  lower  slope,  each 


FIG.  17. — Section  of  timber  dam  on  Schuykill  River,  near  Plymouth,  Pa. 

step  being  8  feet  high  and  20  feet  wide.  In  order  to  form  a  cut-off 
in  the  foundation,  a  concrete  wall  was  built  the  full  length  of  the 
dam.  This  wall  served  also  as  an  anchor  to  the  dam.  The  cribbing 
was  laid  up  in  the  usual  manner,  the  course  resting  on  bedrock 
being  secured  by  anchor  bolts. 

DAM  ON  SCHUYLKILL  RIVER,  NEAR  PLYMOUTH,  PA. 

One  of  the  earliest  constructions  in  the  United  States  was  the 
timber  crib  dam  built  across  Schuylkill  River,  near  Plymouth,  Pa., 
to  obtain  slack  water  for  navigation.  (Fig.  17.)  Edward  Wegmann 
in  his  work  on  dams  gives  the  following : a 

It  was  constructed  on  bedrock  without  the  use  of  a  cofferdam.  The  bottom 
timbers  were  12  by  16  inches  and  were  placed  8  feet  apart,  parallel  with  the 
stream,  and  secured  to  the  rock  bottom  by  2-inch  oak  treenails.  The  succeeding 
courses  of  timber  were  laid  alternately  crosswise  and  lengthwise  with  the 

1  Edward  Wegmann.  Design  and  Construction  of  Dams.  New  York  and  London,  1911 
6.  ed.,  p.  288. 

249,  Pt  II 


30  . 

stream.  All  timbers  were  securely  fastened  together  with  treenails,  no  iron 
bolts  being  used  in  the  structure.  The  upstream  face  of  the  dam  was  covered 
with  timbers  10  inches  thick  placed  close  together.  Until  this  sheathing  was 
laid  the  water  could  pass  freely  between  the  timbers,  as  no  stone  filling  was 
placed  in  the  dam.  The  covering  was  laid  from  both  ends  of  the  dam  until 
only  60  feet  was  left  uncovered  for  the  water  to  pass  through.  The  remaining 
sheathing  was  carefully  cut,  fitted,  and  put  quickly  in  place  by  a  large  force 
of  men  before  the  river  could  rise  so  as  to  interfere  with  the  work.  A  slope 
of  clay  and  stone  was  placed  against  the  upstream  face.  This  dam  stood  for  39 
years,  withstanding  successfully  floods  that  rose  to  a  height  of  11  feet  above  its 
crest. 

TEBASCO  DAM,   COLO. 

This  dam  is  located  in  a  narrow  canyon  on  Lake  Fork  of  Gunnison 
River,  near  Lake  City,  Colo.  It  is  a  bulkhead  constructed  of  timbers 
8  by  8  to  12  by  18  inches  in  size.  It  has  a  maximum  height  of 
138  feet,  length  on  top  20  feet,  with  a  minimum  width  of  38  inches 
and  a  maximum  width  of  74  inches.  The  face  and  back  of  the  dam, 
respectively,  are  approximately  vertical.  The  dam  is  constructed  as 
follows:  The  first  18  feet  in  elevation  was  built  of  12  by  12  inch 
timbers,  laid  in  courses,  six  timbers  to  each  course,  making  a  thick- 
ness of  72  inches.  From  the  eighteenth  to  the  twenty-first  foot 
elevation  four  12  by  18  inch  timbers  with  the  18-inch  edge  vertical 
were  used  to  each  course,  making  a  thickness  of  48  inches  for  this 
part  of  the  dam.  From  the  twenty-first  to  the  fifty-eighth  foot  ele- 
vation the  upstream  timber  of  each  course  was  12  by  12  inches, 
backed  by  36  inches  of  dimension  spruce  not  less  than  8  by  8  inches. 
From  the  fifty-eighth  foot  elevation  to  the  top  of  the  dam,  138  feet, 
the  upstream  timber  of  each  course  was  12  by  12  inch  spruce  backed 
by  24  inches  of  dimension  spruce  not  less  than  8  by  8  inches.  The  first 
18  feet  of  the  dam  is  braced  by  10  by  10  inch  braces  notched  3  inches 
into  the  timbers  of  the  dam  and  laid  one  on  top  of  another  at  an  angle 
of  about  45°.  This  bracing  is  to  prevent  the  base  of  the  dam  sliding. 
All  braces  were  dry,  sound,  red  spruce  and  were  placed  as  follows: 
Four  braces  below  18-foot  level ;  two  braces  from  18  to  100  foot  level ; 
four  braces  from  100  to  138  foot  level  or  top  of  the  dam.  Two 
courses  of  matched  sheathing  with  tar  paper  between  them  were 
placed  on  the  upstream  face  of  the  dam  in  order  to  make  a  tight 
surface.  This  dam  was  constructed  in  1900  for  power  and  milling 
purposes. 

BIG    HOLE    RIVER    DAM,    MONT. 

This  dam  is  owned  by  the  Montana  Power  &  Transmission  Co.  and 
is  located  on  the  Big  Hole  River  about  3  miles  from  Divide  and  21.75 
miles  from  Butte,  Mont.  The  dam  was  originally  built  in  1899,  after- 
wards bought  by  the  above  company  and  reconstructed  in  1901.  It  is 
a  rock-filled  timber  crib  dam  512  feet  long  and  57.5  feet  high,  with  a 
spillway  189  feet  long  equipped  with  flashboards  8  feet  10  inches 

249,  Pt  II 


31 

high.    The  following  description  is  taken  from  an  article  by  M.  S. 
Parker,  C.  E.:1 

The  bottom  of  the  foundation  of  the  dam  is  a  bed  of  stiff,  yellow  clay  with 
bowlders  and  gravel  cemented  together.  The  depth  of  the  foundation  below  the 
original  surface  of  the  ground  varies  at  the  face  of  the  dam  from  12  to  25  feet. 
A  concrete  core  *  *  *  3  feet  9  inches  thick  extends  from  the  foundation  to 
about  6  feet  above  the  original  surface  of  the  ground.  It  follows  the  face  plank- 
ing down  and  is  confined  at  the  back  by  layers  of  2-inch  plank  spiked  to  the 
cribwork.  Concrete  is  also  used  in  front  of  the  face  planking  for  about  10  feet 
above  the  foundation.  The  concrete  is  composed  of  1  part  Utah-Portland  cement, 
2  parts  sharp  sand,  and  5  parts  broken  stone. 

The  excavation  made  in  reaching  the  foundation  is  back  filled  with  concrete 
across  the  river  bottom  for  about  300  feet.  The  remainder  of  this  excavation 
outside  the  planking  is  filled  with  a  semiclay  puddle  rammed  in  layers  to  the 
height  of  the  original  surface  of  the  ground.  Above  this  clay  puddle  and  con- 
crete filling,  on  the  upstream  face  of  the  dam,  is  an  embankment  of  silt  with  a 
slope  of  3  to  1.  This  embankment  is  about  15  feet  high  above  the  concrete  filling 
on  the  face  and  6  feet  high  above  the  clay  puddle.  The  dam  is  constructed  of  10 
by  12  inch  pine  and  fir  timber,  laid  in  continuous  cribs,  8  feet  between  centers. 
The  timbers  are  laid  with  the  12-inch  side  vertical  and  the  cribwork  is  filled 
with  broken  granite.  The  openings  between  the  timbers  are  packed  by  hand 
with  broken  granite  of  irregular  surfaces,  while  the  interiors  of  the  cribs  are 
filled  in  loosely  with  the  same  material  dumped  from  cars. 

The  crest  of  the  dam  is  10  feet  higher  than  the  spillway.  The  spillway  sec- 
tion consists  of  a  series  of  steps  10  feet  high,  the  tread  or  apron  of  each  step 
being  7  feet  wide  and  consisting  of  two  layers  of  timber,  each  10  inches  thick. 
The  high  section  of  the  dam  is  carried  up  in  10-foot  steps  with  vertical  faces, 
which  are  filled  to  a  uniform  slope  from  the  ground  surface.  The  face  of  the 
dam  consists  of  three  layers  -of  plank  securely  spiked  to  the  cribwork.  The 
first  layer  is  of  2-inch  plank,  over  which  is  a  layer  of  3-inch  plank,  breaking 
joints  with  the  first  layer  and  secured  to  the  crib  timbers  with  10-inch  boat 
spikes,  two  spikes  to  every  face  timber.  Over  this  is  a  third  layer  of  2-inch 
plank,  which  also  breaks  joints.  All  planking  is  surfaced  on  one  side  and 
placed  vertical  on  the  face  of  the  dam. 

The  crest  of  the  spillway,  like  the  aprons  above  described,  is  composed  of  two 
layers  of  10-inch  lumber  with  seams  calked  with  oakum.  All  timbers  in  the 
cribwork  and  aprons  are  securely  bolted  with  drift  bolts  f  inch  square,  20 
and  28  inches  long.  Two  28  and  three  20  inch  bolts  were  used  in  each  16 
feet  of  timber.  The  face  planking  is  relied  upon  to  prevent  leakage,  and 
the  granite  filling  is  intended  for  weight  only.  Water  is  taken  from  the 
dam  through  gates  into  a  large  wooden  flume  or  forebay  28  feet  in  depth  and 
15  feet  in  width,  from  which  five  steel  penstocks  lead  to  five  66-inch  turbines 
of  special  design. 

A  tunnel  is  cut  through  the  ledge  on  the  north  side  to  be  used  for  a  waste- 
way  to  drain  down  the  pond.  This  wasteway  is  regulated  by  a  system  of  gates 
arranged  to  control  the  flow  of  water  to  the  power  house. 

The  following  statement  of  costs  includes  the  prices  paid  for  the  hauling  of 
all  material  necessary  for  the  work,  such  as  cement,  lumber,  and  iron  from  the 
railway  station  to  the  dam,  a  distance  of  3  miles . 

1  Report  M.  S.  Parker,  Jour.  Assoc.  Engin.  Socs.,  22  (1899),  No.  4,  pp.  175-195. 
249,  Pt  II 


32 

Contract  prices  for  different  kinds  of  ivork,  Biy  Hole  River  Dam,  Mont. 

Earth  and  loose  rock  excavation  below  water,  per  cubic  yard-  $1.  00 

Earth  and  loose  rock  excavation  above  water,  per  cubic  yard-  .  40 

Stone  filling  in  crib .75 

Solid  rock  excavation 1.00 

Stone  masonry,  cement  furnished  by  company,  per  cubic  yard-  5.  70 
Concrete  above  water,  cement  furnished  by  company,  per 

cubic  yard 4.05 

Concrete  below  water,  cement  furnished  by  company,  per 

cubic  yard ± , 5.  88 

Back  filling  of  earth .25 

Lumber  in  place  (for  labor  only),  per  1,000 10.00 

A  flood  occurred  April  16-25,  1898,  the  water  reaching  its  maxi- 
mum flood,  3,500  feet  per  second,  on  April  18,  this  being  sufficient  to 
cause  a  flow  of  several  feet  above  the  spillway.  A  partial  failure  of 
the  dam  occurred  at  this  time,  the  upper  part  of  the  central  portion 
of  the  dam  being  pushed  downstream,  the  maximum  movement  of 
the  crest  from  original  position  being  13  feet. 

Several  causes  were  attributed  for  this  failure.  It  was  thought  by 
some  that  the  overthrowing  pressure  of  the  water,  together  with  the 
weight  of  the  section  of  the  dam,  brought  an  undue  pressure  upon 
the  timbers  of  the  cribwork  at  their  intersections.  The  laying  of 
the  dry  wall  of  rocks  between  the  timbers  gave  an  insufficient  bearing 
surface  to  resist  the  pressure  under  the  conditions  mentioned. 

The  spillway  for  this  dam,  as  originally  designed  by  the  con- 
sulting-engineer, was  to  go  through  solid  rock  around  one  end  of 
the  structure,  but  the  members  of  the  company  which  owned  the  dam 
altered  this  plan.  This  incident  shows  the  advisability  of  a  State 
engineer  having  to  pass  on  all  plans  for  such  structures.  The  par- 
tial failure  of  this  dam  would  probably  have  been,  averted  if  such  a 
regulation  had  been  effective  in  Montana  at  this  time. 

The  binding  of  the  timbers  together  and  the  thorough  settling  of 
the  filling  of  this  dam  when  the  water  rushed  into  it  probably  saved 
its  complete  failure.  The  structure  has  been  largely  rebuilt,  30  or 
40  feet  having  been  removed  from  the  top  and  replaced  and  the 
balance  strengthened. 

BUTTE  CITY  WATER  CO.'S  DAM,   MONTANA. 

Two  considerations  led  the  engineer  in  charge  of  this  work  to 
choose  the  rock-filled  crib  type  of  dam.  Masonry  was  too  expensive, 
and  there  were  no  suitable  materials  in  that  vicinity  for  building  an 
earthen  dam.  The  dam  is  319  feet  long  on  the  crest  and  42  feet  high, 
including  the  spillway  and  the  cribwork.  It  is  built  of  round  fir 

249,  Pt  II 


U.  S.  Dept.  of  Agr.,  Bui.  249,  Pt.  II,  Office  of  Expt.  Stations.     Irrigation  Investigations.  PLATE  V. 


FIG.  1.— BULKHEADS  AND  CREST  OF  SPILLWAY,  FROM  UPSTREAM  SIDE,  LYONS  DAM,  CAL. 


FIG.  2.— DIVERSION  DAM  AND  FLUME  BELOW  LYONS  DAM,  SHOWING  MAIN  DAM  IN 
DISTANCE. 


U.  S.  Dept.  of  Agr.,  Bui.  249,  Pt.  II,  Office  of  Expt.  Stations.     Irrigation  Investigations.  PLATE  VI. 


FIG.  1.— LAKE  KEECHELUS  CRIB  DAM  DURING  CONSTRUCTION,  DOWNSTREAM  VIEW. 


FIG.  2.— THE  COMPLETED  DAM,  LAKE  KEECHELUS,  WASH.,  SHOWING  SPILLWAY  AND 
BULKHEAD. 


33 

logs  in  cribs  8  feet  square.  These  logs  were  not  less  than  7  inches 
in  thickness  at  the  small  ends  and  were  all  stripped  of  bark.  At  all 
intersections  and  at  every  contact  a  three-fourths  inch  drift  bolt  was 
driven  to  bring  the  logs  together.  Fillers  were  inserted  between  the 
logs,  running  in  the  direction  of  the  pressure,  as  shown  in  figure  18. 
These  fillers  were  firmly  held  in  place  by  drift  bolts  and  wrere  put 
in  to  make  a  greater  bearing  surface  to  withstand  the  pressure  and 
also  to  prevent  the  cross  logs  from  rolling  when  the  pressure  was 
received.  At  each  end  of  the  structure  the  logs  were  anchored  to 
bedrock  when  possible. 

The  upper  face  of  the  dam  has  a  slope  of  16  feet  horizontal  to  39 
feet  vertical;  the  lower  face  24  feet  horizontal  to  42  feet  vertical. 
The  water  face  is  sheathed  with  2-inch  planking  laid  double  and 
breaking  joints  to  make  it  water-tight.  This  lining  extends  along 
the  slope  of  the  face  to  the  top  of  the  core  wall,  thence  to  bedrock 


FIG.  18. — Butte  City  Water  Co.'s  crib  dam,  for  Reservation  No.  2,  Basin  Creek,  Mont. 

in  front  of  the  concrete  core  wall.  It  was  the  intention  of  the  en- 
gineer to  nail  battens  over  the  seams  as  the  water  surface  lowered 
in  the  winter  in  order  to  reduce  the  leakage.  The  logs  forming  the 
water  face  were  hewn  to  a  true  surface  to  receive  the  sheathing,  the 
lowest  one  being  embedded  in  the  concrete  core  to  form  the  knuckle 
where  the  slope  joined  the  face  of  the  core  wall. 

The  cribs  were  filled  with  broken  rock  upon  which  decomposed 
granite  was  flushed  so  as  to  thoroughly  fill  all  interstices.  Great 
care  was  exercised  to  see  that  every  part  of  the  crib  was  thoroughly 
filled.  The  material  was  first  placed  in  thin  layers  and  spread  by 

249,  Pt  II 


34 

hand.  A  liberal  amount  of  water  was  then  used  to  settle  it  thor- 
oughly and  to  flush  the  decomposed  granite  into  the  interstices.  The 
concrete  core  wall  was  3  feet  8  inches  thick  and  extended  along  the 
inner  toe  of  the  cribwork  to  bedrock.  The  double  2-inch  sheeting 
on  its  upper  side,  previously  mentioned,  was  built  to  prevent  any 
leakage  under  the  structure.  The  concrete  was  made  in  the  propor- 
tion of  5  parts  broken  rock,  3  parts  sand,  and  1  part  cement,  and  was 
carefully  rammed  into  place.  The  wall  was  carried  about  1  foot  above 
the  base  of  the  cribwork  to  support  the  lower  log  which  formed  the 
knuckle  of  the  sheeting.  Where  the  sloping  face  of  planking  joined 
the  vertical  sheeting,  an  additional  plank  was  spiked  over  the  joint 
horizontally,  and  all  seams  were  carefully  calked  with  oakum  and 
poured  with  hot  asphalt.  A  puddle  fill  of  earth  and  gravel  mixed 
was  then  made  against  the  dam,  extending  about  8  feet  above  the 
knuckle  and  10  feet  upstream.  The  outside  seams  to  the  top  were 
then  loosely  calked  with  oakum.  The  calking  and  puddling  about 
the  knuckle  were  left  until  the  last  when  most  of  the  settling  had 
taken  place.  The  work  on  this  dam  was  authorized  in  the  spring  of 
1898  and  the  reservoir  was  completed  about  July  1  of  that  year.1 

CANYON  FERRY   DAM,   MONT. 

The  Canyon  Ferry  Dam  was  built  in  1898  across  the  Missouri 
River  near  Helena,  Mont.,  for  the  Helena  Water  &  Electric  Power 
Co.  The  plans  for  this  dam  were  prepared  by  the  consulting  engi- 
neer of  the  company.  The  following  data  is  taken  largely  from 
Wegmann's  work  on  the  construction  of  dams.2 

The  dam  consists  of  timber  cribs  filled  with  stone.  It  is  485  feet 
long  and  29  feet  high.  The  cribwork  for  this  dam  was  built  to  con- 
form to  the  bed  of  the  river,  which  is  composed  of  a  compact  mixture 
of  gravel  and  sand  and  is  practically  impervious.  Both  above  and 
below  the  timber  cribbing  there  is  a  row  of  triple  lap  sheet  piling 
made  of  3  by  12-inch  planking,  stiffly  bolted  together  and  driven  12 
feet  below  the  level  of  the  bed  of  the  river.  Where  the  material 
was  hard  the  piling  was  driven  to  a  satisfactory  refusal,  or  until  there 
was  danger  of  splitting  the  top  of  the  pile.  To  further  strengthen 
the  dam,  a  double  row  of  round  piling  was  driven  at  the  toe  of  the 
apron,  the  piles  being  3  feet  centers.  This  precaution  was  to  prevent 
the  toe  of  the  apron  from  being  lifted  at  times  of  high  water. 

The  timbers  of  the  dam  are  fastened  together  with  iron  drift  bolts 
20  to  30  inches  long.  To  break  the  force  of  the  water  and  prevent 

*Data  largely  from  report  of  Eugene  Carroll,  Jour.  Assoc.  Engin.  Socs.,  22  (1899), 
No.  4,  pp.  196-204. 

2  Edward  Wegmann.  Design  and  Construction  of  Dams.  New  York  and  London,  1911, 
6.  ed.,  p.  293. 

249,  Pt  II 


35 

it  from  scouring  out  the  gravel  at  the  foot  of  the  apron,  the  down- 
stream face  of  the  dam  was  formed  originally  of  three  steps  (fig.  19). 
First,  there  was  a  timber  apron  14  feet  wide,  then  two  steps 
with  10  feet  rises  and  treads,  then  a  rise  of  7£  feet  to  the  crest. 
The  rises  were  inclined  on  a  slope  of  about  one-third  to  1.  The 
steps  were  covered  with  two  courses  of  3-inch  plank  lap- jointed. 
The  back  of  the  dam  was  covered  in  a  similar  manner  with  2-inch 
plank.  An  earthen  slope  riprapped  at  the  top  was  placed  against 
the  back  of  the  dam,  and  below  the  dam  large  rocks  were  placed  to 
bring  the  top  flush  with  the  level  of  the  apron.  This  was  extended 
for  a  distance  of  25  feet  and  held  in  place  by  a  double  row  of  round 
piles  on  the  downstream  side.  The  timber  dam  is  founded  on  a  bed 
of  gravel  and  granite  sand,  which  is  almost  impervious  to  water. 
Masonry  abutments  were  built  on  both  ends  of  the  crib  dam  to  a 


FIG.  19. — Section  of  Canyon  Ferry  Dam,  Mont.,  as  reconstructed. 

height  of  12£  feet  above  its  crest  or  flow  line.  On  the  east  bank  an 
earthen  dam  285  feet  long  with  a  masonry  core  wall  and  slopes  of 
2  to  1  and  1|  to  1,  respectively,  on  the  upstream  and  downstream 
sides,  was  built  to  the  hillsides.  (PI.  VII,  fig.  1.)  The  top  of  the 
dam  is  at  the  level  of  the  top  of  the  abutments. 

Soon  after  the  dam  was  completed  a  heavy  freshet  occurred  in 
which  5  feet  of  water  passed  over  its  crest.  With  this  depth  the 
sheet  of  water  after  passing  over  the  first  step  cleared  the  other  two 
and  struck  the  apron  and  protecting  riprap  with  such  force  as  to 
destroy  them  both  for  a  large  portion  of  the  length  of  the  dam. 
With  the  riprap  gone,  the  stream  began  to  scour  and  undermine  the 
dam,  causing  it  to  settle,  finally,  to  1  foot  below  its  original  height 
and  nearly  6  feet  downstream  out  of  line.  (PI.  VII,  fig.  2.)  The 
dam  was  repaired  with  new  cribbing  heavily  anchored  and  tied 
together.  A  timber  apron  49  feet  long  was  placed  on  the  downstream 

249,  Pt  II 


36 

side  of  the  dam,  and  two  slopes  (fig.  20)   were  substituted  for  the 
three  steps,  the  first  being  39  feet  long  and  the  second  60  feet.     About 


FIG.  20. — Canyon  Ferry  Dam,  showing  the  reconstructed  portion  as  well  as  part  of  the 

old  dam. 

8,000  yards  of  rock  was  used  in  the  reconstruction  and  1,500,000  feet 
of  lumber.  f 

During  the  high  water  of  1899,  7^  feet  of  water  passed  over  the 
reconstructed  dam  without  injury  to  the  structure. 

249.  Pt  II 


ROCK-FILL  DAMS. 


TYPES  AND  DESIGNS  OF  ROCK-FILL  DAMS. 

Rock-fill,  often  called  loose  rock,  dams  have  been  built  quite  exten- 
sively in  the  West  during  the  past  half  century.  The  abundance  of 
rock  along  the  streams,  the  high  price  of  other  building  materials, 
and  the  lack  of  good  transportation  facilities  have  induced  water 
companies  of  all  kinds  to  make  use  of  this  type  of  dam.  The  greater 
part  of  such  structures  consists  of  loose  rock,  either  dumped  into 
position  or  placed  by  derricks.  The  mass  and  weight  of  the  rocks 
provide  the  necessary  stability  against  water  pressure  and  the  re- 
sulting tendency  of  the  dam  to  overturn  or  slide.  Such  dams  are 
rendered  impervious  either  by  the  use  of  earth,  lumber,  concrete,  or 
steel.  The  size  of 
the  dam  and  the 
ultimate  cost  of  ob- 
taining and  plac- 
ing the  materials 
determine  which  is 
preferable  in  each 
case. 

If  suitable  rock 

and  earth  can  be  obtained  in  close  proximity  to  the  dam  site,  a  safe 
and  durable  structure  can  be  built  cheaply  in  this  way. 

The  site  for  the  foundation  should  be  stripped  of  all  organic 
matter  and  should  consist  of  solid  rock,  hardpan,  or  other  unyielding 
impervious  material.  The  passage  of  percolating  water  along  the 
natural  surface  is  checked  by  cutting  a  trench  across  the  foundation 
somewhere  near  the  inner  toe  of  the  dry  rubble  wall  and  building 
therein  a  concrete  wall  having  its  top  some  distance  above  the  natural 
surface.  A  cross  section  of  this  type  of  dam  is  shown  in  outline  in 
figure  21.  The  earth  portion  of  the  dam  may  be  built  in  one  of  the 
several  ways  outlined  in  Part  I  of  this  bulletin ; l  that  is,  by  depositing 
in  layers,  moistening,  and  compacting;  by  dumping  into  water;  or 
by  sluicing  into  place.  The  latter  methods  are  to  be  preferred  where 


FIG.  21. — Section  of  iypica£.rock-fill  <jam. 


249,  Pt  II 


1  U.  S.  Dept.  Agr.,  Office  Expt    Stas.  Bui.  249,  pt.  1. 


(37) 


38 


feasible,  as  greater  water-tightness  is  assured  by  their  use,  since  the 
soft  mud  borne  by  the  water  is  deposited  in  the  open  spaces  of  the 
loose  rock,  particularly  along  the  upstream  face.  The  earth  slope 
is  riprapped  as  indicated  in  the  same  figure. 

In  districts  where  lumber  is  cheap  and  abundant,  rock-fill  dams 
are  made  reasonably  water-tight  by  placing  two  thicknesses  of  plank 
on  the  upstream  face.  The  planks  are  usually  spiked  to  stringers 
which  extend  up  and  down  the  slope,  which  in  turn  are  bolted  to 
horizontal  timbers  set  in  the  rock  fill.  This  practice  was  common  in 
the  time  of  hydraulic  mining  in  California  and  is  illustrated  by 
figure  22.  In  rarer  cases  the  planks  are  spiked  to  a  framework 

of  timber  placed  vertically 
near  the  center  of  the  dam. 
More  or  less  concrete  is 
now  used  in  the  founda- 
tion trenches  of  all  rock-fill 
dams,  and  frequently  the 
same  material  is  relied 
upon  for  the  building  of 
an  impervious  core  wall. 
In  the  latter  case  the  core 
wall  is  usually  located  near 
the  center  of  the  structure. 
The  chief  objections  to  the 
use  of  concrete  core  walls 
in  rock-fill  dams  is  their 
tendency  to  crack,  on  ac- 
count of  variations  in  tem- 
perature, particularly  if 
the  .wall  is  thin.  It  should  be  remembered  that  such  walls  are 
more  exposed  to  changes  in  temperature  than  are  core  walls  in 
earthen  embankments,  and  when  this  material  is  used  for  such  a  pur- 
pose provision  should  be  made  for  expansion  and  contraction  joints. 
A  few  dams  of  the  rock-fill  type  are  faced  with  concrete  on  the  up- 
stream side,  but  such  a  facing  is  liable  to  be  ruptured  by  the  settle- 
ment of  the  loose  rock,  no  matter  how  carefully  it  is  placed. 

The  use  of  steel  plates  to  render  rock-fill  dams  water-tight  origi- 
nated in  California  and  has  been  used  to  a  limited  extent  in  other 
parts  of  the  West.  When  the  steel  core  is  thoroughly  protected  from 
erosion,  punctures,  and  fractures,  this  type  of  dam  compares  favor- 
ably with  masonry  dams  in  durability  and  stability,  and  also  with 
cheaper  types  of  dams  in  first  cost.  The  conditions  best  adapted  to 
this  kind  of  construction  are  a  deep,  narrow  stream  channel  in  solid 
rock,  where  an  abundance  of  rock  can  be  cheaply  blasted  and  thrown 
into  the  chasm  or  readily  transported  to  the  site.  These  conditions 

249,  Pt  II 


FIG.   22. — Sketch  showing  method  commonly  used 
for  facing  rock-fill  dam  with  timber. 


39 

are  common  in  the  more  elevated  portions  of  the  arid  region,  and 
therefore,  since  this  type  of  dam  is  likely  to  be  used  extensively  in 
the  future,  considerable  space  is  here  given  to  a  discussion  of  its 
principal  features. 

In  designing  dams  of  loose  rock,  due  consideration  should  be  given 
to  the  fact  that  all  such  structures  settle  more  or  less  during  con- 
struction and  for  some  time  thereafter.  The  amount  of  this  settle- 
>  ment  depends  upon  the  height  of  the  dam,  the  character  of  the  rock, 
and  the  way  it  is  placed.  Under  ordinary  conditions  a  dam  100  feet 
high  is  likely  to  settle  2  to  3  feet.  Provision  must  therefore  be  made 
to  permit  the  loose  rock  to  consolidate  without  injury  to  other  parts 
of  the  structure.  In  combination  dams  of  earth  and  loose  rock  there 
is  little  danger  from  this  cause.  The  same  is  true  of  timber-faced 
dams  of  low  or  medium  height,  as  the  loose  rOck  usually  has  time 
to  settle  before  the  lumber  sheeting  is  put  on.  On  the  other  hand, 
in  the  case  of  high  dams  rendered  water-tight  by  either  steel  or 
concrete,  or  a  combination  of  the  two,  greater  care  must  be  exercised. 
When  the  steel  or  other  impervious  lining  is  placed  on  the  upstream 
face  great  risk  is  incurred,  as  the  settling  of  the  loose  rock  is  apt  to 
rupture  the  lining  or  leave  it  without  adequate  support.  Danger 
from  this  cause  can  be  readily  avoided,  however,  by  having  the  steel 
or  concrete  core  in  a  vertical  position  near  the  center  of  the  structure. 

It  is  frequently  contended  that  the  upstream  face  of  the  dam  should 
be  made  water-tight  in  order  to  take  advantage  of  the  full  weight 
of  the  rock.  Otherwise,  it  is  claimed,  that  portion  of  the  structure 
between  the  upstream  face  and  the  core  wall  would  be  submerged 
and  its  effective  weight  decreased  to  the  extent  of  the  weight  of  water 
displaced.  Notwithstanding  this  disadvantage,  the  safety  at  least  of 
all  high  dams  with  steel  or  concrete  core  walls  requires  that  the  core 
wall  be  placed  near  the  center.  The  factor  of  safety  in  such  struc- 
tures is  necessarily  so  large  that  the  loss  of  weight  due  to  flotation 
is  small  in  comparison  with  the  weight  of  the  entire  structure. 

A  core  wall  placed  near  the  center  of  the  dam  is  not  easily  reached 
for  repairs  or  renewals,  and  for  this  and  other  reasons  it  should  be 
thoroughly  protected.  A  heavy  asphalt  coating  backed  by  two  12-inch 
walls  of  sand  concrete  was  used  to  protect  the  steel  sheeting  in  the 
Lower  Otay  and  other  rock-filled  dams  built  in  San  Diego  County, 
Cal.  One  of  the  writers  in  designing  the  East  Canyon  Dam  in  Mor- 
gan County,  Utah,  substituted  a  4-inch  layer  of  asphalt  concrete  for 
the  12-inch  wall  of  sand  concrete.  His  reasons  for  making  this 
change  were  to  secure  greater  elasticity  in  the  core  wall  and  to  more 
completely  protect  the  steel  plates  against  erosion,  punctures,  and 
fractures.  The  cost  was  also  considerably  less.  This  protected  steel 
core  has  now  been  in  use  for  13  years,  and  has  shown  no  signs  of 
deterioration. 

249,  Pt  II 


40 


When  conditions  are  favorable  rock-fill  dams  with  steel  cores  can 
be  built  very  economically.  If  possible,  the  outlet  should  be  made 
by  tunneling  through  the  rock  ledge  at  one  end  of  the  site.  While 
this  work  is  in  progress  a  trench  may  be  excavated  to  bedrock  across 
the  canyon  and  a  heavy  wall  of  cement  concrete  built  therein.  Having 
completed  the  foundation  and  the  outlet,  the  construction  force  is 
ready  to  fill  the  entire  chasm  with  loose  rock.  This  often  can  be 
done  by  heavy  blasting  on  the  faces  of  the  cliffs  above  the  top  of 
the  dam.  The  top  of  the  concrete  wall  is  protected  by  timbers.  On 
a  favorable  site  rock  can  be  shot  into  the  stream  channel  for  a  few 
cents  a  yard.  When  thrown  down  by  the  above  method,  the  frag- 
ments vary  from  small  pieces  to  large  masses  containing  several  hun- 
dred cubic  yards,  and,  although  not  consolidated,  they  give  the  struc- 
ture stability  and 
afford  an  effective 
barrier  to  the  force 
of  escaping  water 
in  case  of  a  break. 
When  loose  rock 
can  be  so  cheaply 
secured,  the  ques- 
tion of  proper  di- 
mensions, slopes, 
and  the  like  is  of 
minor  importance, 
and  it  is  necessary 
only  to  throw  down 
such  an  excess  of 
rock  as  will  make 
the  structure  abso- 
lutely safe.  This 
being  first  done,  a  channel  for  inserting  the  steel  core  is  then  exca- 
vated directly  above  the  concrete  wall  through  the  mass  of  loose  rock. 
This  channel  should  be  of  sufficient  width  to  admit  the  building  of  a 
derrick-placed  wall  on  each  side  of  the  steel  sheeting  and  its  cushions 
of  asphalt  concrete.  To  allow  the  rock  to  settle  without  disturbing 
the  asphalt  concrete,  wooden  forms  should  be  inserted  between  the 
rock  wall  and  the  concrete,  making  a  division  wall  between  the 
asphalt  concrete  and  the  loose  rock  fill  on  either  side.  By  the  time 
the  boards- decay,  the  loose  rock  will  have  become  consolidated,  and 
the  dry  walls  on  each  side  will  gradually  settle  against  the  asphalt 
concrete  cushion.  The  sketch  shown  in  figure  23  illustrates  the 
manner  of  building  and  protecting  the  steel  plates. 

The  subjects — outlets,  wasteways,  concrete  core  walls,  and  slope 
protection  for  earth  embankments — are  treated  in  detail  in  Part  I 

249,  Pt  II 


FIG.  23.- -Section  of  concrete  base  with  steel  core  protected  by 
asphalt  concrete  encased  in  wooden  forms. 


PLATE  VII. 


FIG.  1.— METHOD  OF  CONSTRUCTING  EARTH  FILL  AT  END  OF  CRIB  DAM,  CANYON  FERRY 
DAM,  MONT. 


FIG.  2.— CANYON  FERRY  DAM,  BEFORE  RECONSTRUCTION. 


U.  S.  Dept.  of  Agr.,  Bui.  249,  Pt.  II,  Office  of  Expt.  Stations.     Irrigation  Investigations.  PLATE  VIII 


FIG.  1.— EAST  CANYON  DAM,  UTAH,  SHOWING  TEMPORARY  SPILLWAY. 


FIG.  2.— SAME,  SHOWING  STEEL  CORE  PROJECTING,  AND  SPILLWAY  ON  LEFT,  AUGUST, 

1900. 


41 

of  this  bulletin,1  and,  as  many  of  the  points  therein  discussed  are 
equally  applicable  to  the  construction  of  loose-rock  dams,  the  reader 
is  referred  thereto  for  information  along  these  lines. 

A  few  somewhat  typical  examples  of  loose-rock  dams  are  described 
and  illustrated  in  the  following  paragraphs : 

THE  LOWER  OTAY  DAM,  CAL. 

The  Lower  Otay  Dam  is  located  about  22  miles  southeast  of  San 
Diego,  Cal.  This  type  of  rock-fill  dam  is  the  pioneer  of  the  kind, 
the  idea  originating  with  the  president  of  the  Southern  California 
Mountain  Water  Co.  It  was  originally  intended  to  build  a  rubble 
masonry  dam,  and  in  carrying  out  this  plan  an  excavation  65  feet 
wide  and  85  feet  long  was  cut  from  the  bed  of  the  stream  down  to 
bedrock,  a  distance  of  20  feet.  This  trench  was  filled  with  rubble 
masonry  laid  in  cement  and  raised  to  a  height  of  28  feet  above  bed- 
rock, or  8  feet  above  the  stream  bed.  The  loose  rock  and  earth  were 
stripped  from  the  slope  at  the  east  end  of  the  dam,  but  when  it  came 
to  excavating  the  earth  on  the  west  end  the  distance  to  bedrock  was 
so  great  as  to  make  the  building  of  a  masonry  dam  impracticable. 
The  plan  of  constructing  a  masonry  dam  was  therefore  abandoned 
and  a  loose-rock  dam  with  a  steel  core  adopted. 

At  the  side  walls  of  the  canyon  a  narrow  cut  or  excavation  was 
made  through  the  loose  rock  to  solid  rock,  and  a  trench  4  feet  in 
width  was  extended  from  this  excavation  into  the  bedrock  for  a 
distance  of  4  feet.  This  trench  was  located  on  the  axis  of  the  loose- 
rock  dam,  but  only  10  feet  above  the  lower  line  of  the  masonry  wall. 
On  top  of  the  masonry  wall  at  the  center  line  of  the  trench  a  T  iron 
was  anchored  by  1-inch  bolts  leaded  fast  in  holes  drilled  in  the 
masonry.  The  T  iron  was  punched  for  f-inch  rivets  spaced  3  inches 
center  to  center  to  coincide  with  the  punching  of  the  steel  plates. 
These  plates  were  in  two  sizes,  5  by  17  feet  and  8  by  20  feet,  and 
ranged  in  thickness  from  0.259  to  0.34  inch  (No.  3  to  No.  0  Birming- 
ham gauge).  After  riveting,  the  edges  of  the  sheets  were  split  and 
calked,  the  sheets  having  been  placed  so  that  the  calking  could  be 
done  on  the  water  side.  The  steel  was  then  cleaned  and  a  coating  of 
a  soft  asphaltum  (F  grade,  Calif ornia-Alcatraz  asphaltum)  was 
applied  with  brushes.  To  prevent  the  asphaltum  from  flowing, 
strips  of  burlap  were  placed  on  the  asphaltum,  each  strip  overlapping 
the  one  below  about  3  inches.  The  burlap  was  brushed  on,  while  the 
asphaltum  was  still  warm,  with  a  broom  used  in  the  same  manner 
as  a  paper  hanger  uses  a  brush  in  smoothing  wall  paper.  A  coat  of 
C-grade  asphaltum  was  then  applied  on  the  burlap  in  the  same 
manner  as  the  first  coat,  F  grade.  A  coating  made  in  the  latter  way 

1  U.  S.  Dept.  Agr.,  Office  Expt.  Stas.  Bui.  249,  pt.  1. 
249,  Pt  II 


42 

makes  a  tough,  hard  covering  that  will  stand  on  a  vertical  surface 
even  on  a  warm  day  under  the  direct  rays  of  the  sun. 

To  protect  the  steel  from  injury  by  the  rock  used  in  the  body  of 
the  dam,  a  narrow  wall  of  concrete  consisting  of  cement  and  sand  was 
built  up  on  each  side  of  it.  Commencing  with  the  first  course  of  steel 
on  top  of  the  masonry  dam,  this  wall  was  made  8  feet  in  thickness 
each  side  of  the  core,  but  narrowed  gradually  until  at  a  height  of 
8  feet  from  the  T  iron  it  was  1  foot  in  thickness  on  each  side.  This 
latter  thickness  was  maintained  from  this  point  to  the  top  of  the  dam. 
To  prevent  leakage  around  the  ends  of  the  core  the  masonry  wall  was 
made  wider  where  it  joined  the  bedrock.  From  about  20  feet  from 
the  sides  of  the  canyon,  where  the  narrow  trench  had  been  cut  into 
the  bedrock,  the  masonry  wall  was  gradually  widened  to  a  width  of 
20  feet  where  it  joined  the  rock  side  walls.  The  masonry  wall  was 
brought  up  to  within  6  inches  of  the  top  of  the  steel  before  another 
course  of  plates  was  riveted  on. 

The  mortar  used  was  made  of  best  English  Portland  cement  mixed 
with  clean,  washed  river  sand.  The  proportions  used  were  1  part 
cement  to  4  parts  sand  for  the  end  wralls  and  for  the  narrow  wall  up 
to  a  height  of  70  feet,  and  1  part  cement  to  6  parts  sand  for  the  bal- 
ance of  the  narrow7  wall.  The  strength  of  concrete  composed  of  1 
part  cement  and  6  parts  coarse  sand  is  much  below  that  of  ordinary 
concrete  made  up  of  cement,  sand,  and  gravel  or  broken  rock.  It  is 
therefore  not  clear  why  this  mixture  was  used  in  the  upper  portion 
of  the  core  wall.  The  mixing  of  the  mortar  was  done  with  shovels 
on  platforms  located  at  each  end  of  the  dam  and  near  the  top.  From 
this  platform  the  mortar  was  sent  down  in  a  chute  to  whatever  height 
it  was  being  used. 

To  hold  this  narrow  wall  in  place  until  hardened,  2  by  6  inch  pieces 
were  set  upright,  12  inches  from  the  steel  core,  as  may  be  seen  in 
figure  24.  One-inch  boards  wrere  nailed  to  these  pieces,  leaving  a 
space  of  12  inches  for  the  masonry.  The  uprights  were  set  opposite 
each  other  and  tied  together  by  nailing  on  another  piece  of  2  by  6 
inches  with  its  edge  resting  on  top  of  the  steel.  On  top  of  this  was 
laid  the  plank  for  a  runway  for  the  men  wheeling  mortar  from  the 
chute  to  wherever  needed.  (Fig.  24.) 

The  steel  sheets  were  brought  as  close  as  possible  to  the  uneven  rock 
of  the  side  walls,  without  having  to  cut  them,  and  riveted  to  bolts 
leaded  into  the  rock  walls.  Where  not  riveted  to  anchor  bolts,  short 
drift  bolts  of  f-inch  iron  were  put  through  the  rivet  holes  in  the  ends 
of  the  sheet.  These  prevented  the  sheet  plate  from  pulling  out  of 
the  masonry. 

The  rock  placed  in  the  embankment  was  a  hard  porphyry,  easily 
broken,  but  very  hard  to  drill.  The  first  quarrying  was  done  by  drill- 

249,  Pt  II 


43 


ing  holes  from  10  to  20  feet  in  depth  for  each  blast.  This  method 
was  found  to  be  very  expensive  and  too  slow.  It  was  decided  to  run 
a  drift  or  tunnel  into  the  hill  and  make  a  large  blast.  The  drift  was 
driven  for  a  distance  of  50  feet  and  then  branched  into  a  Y.  The 
upper  extremities  of  the  Y  were  enlarged  to  make  powder  chambers. 
The  chamber  on  the  right  side,  or  towarc1  the  dam,  held  2  tons  of 
Judson  powder,  a  low-grade  nitroglycerin  compound,  and  the  other 
chamber  held  4  tons.  After  the  powder  was  in  place  and  the  two 
chambers  connected  with  electric  wires,  the  drift  was  completely 
blocked  with  earth  and  sand.  The  wires  were  then  connected  to  an 
exploding  dynamo,  which  produced  the  necessary  spark,  and  the  blast 
was  set  off,  throwing  down  about  75,000  cubic  yards  of  rock.  While 
this  rock  was  being  placed  in  the  dam  a  second  blast  was  being  pre- 
pared which  would 
furnish  enough  rock 
to  complete  the  dam. 
This  second  blast  con- 
sisted of  a  shaft  115 
feet  deep,  in  which 
two  drifts  at  a  depth 
of  85  feet  and  two  at 
the  bottom  were  run 
out  at  right  angles 
to  the  shaft.  Fifteen 
tons  of  powder  were 
used,  the  greater  part 
being  in  the  bottom 
chambers.  All  loose, 
hanging  rock  on  the 
face  of  the  quarry 
was  knocked  down 
after  each  large  blast,  so  the  danger  of  rock  rolling  down  on  the 
men  was  reduced  to  a  minimum. 

The  rock  was  brought  from  the  quarry  by  means  of  a  Lidger- 
wood  cableway,  having  a  span  of  950  feet  and  capable  of  handling 
a  safe  load  of  10  tons.  The  cable  on  which  the  carriage  traveled 
rested  on  two  towers,  one  130  feet  high  and  the  other  60  feet.  This 
difference  in  height  was  due  to  the  difference  in  elevation  where  the 
two  towers  stood.  The  cable  crossed  the  dam  at  an  angle  of  about 
60°,  the  main  cable  being  60  feet  above  the  crest  of  the  dam.  The 
rock  was  delivered  on  the  dam  by  this  cableway  (fig.  25),  and  until 
the  dam  reached  a  height  of  75  feet  it  was  distributed  wherever 
needed  by  derricks.  The  length  of  the  dam  at  this  point  being  so 
great  that  it  could  not  be  handled  without  transferring  from  one 
derrick  to  another,  another  cableway  was  erected  to  take  the  place 

249,  Pt  II  s 


PIG.  24. — Corewall  of  Lower  Otay  Dam,  Cal.,  under  con- 
struction. 


44 

of  the  derricks.  This  also  was  a  Lidgerwood  cableway,  but  the 
towers  were  built  on  heavily  ballasted  cars  on  wheels  which  could  be 
moved  on  tracks  from  a  point  15  feet  below  the  core  to  a  point  the 
same  distance  above,  the  cable  between  these  towers  being  parallel  to 
the  axis  of  the  dam.  This  cable  was  only  30  feet  above  the  dam, 
thus  allowing  sufficient  room  for  loads  to  be  carried  above  it  by 
cableway  No.  1.  In  the  quarry  a  derrick  was  placed  so  that  a  load 
could  be  picked  up  in  any  part  of  the  quarry  and  set  down  directly 
under  the  cable. 

A  loaded  skip  would  be  handled  in  the  following  manner:  First, 
the  derrick  would  pick  up  the  loaded  skip  and  set  it  down  under 
cableway  No.  1  and  take  an  empty  skip  back  to  be  reloaded.  Cable- 
way  No.  1  would  then  hoist  the  load  and  carry  it  on  the  dam,  where 


PIG.  25. — Lower  Otay  Dam — two  cableways  delivering  rock  from  quarry. 

the  chains  would  be  unhitched  from  this  and  hitched  to  an  empty 
skip  to  be  taken  back  to  the  quarry.  Cableway  No.  2  would  then 
hoist  the  load,  carry  it  wherever  needed,  spill  it,  and  set  the  skip 
back  under  cableway  No.  1  before  the  latter  had  returned  with  an- 
other load.  In  this  way  the  cableways  and  derrick  would  all  be  at 
work  without  interfering  with  each  other.  As  high  as  225  loads 
were  handled  in  10  hours,  and  the  daily  average  of  200  loads  was 
made  for  several  weeks  at  a  time.  This  number  could  have  been 
increased  if  the  quarry  had  been  above  the  top  of  the  dam.  In  the 
present  case  the  level  of  the  bottom  of  the  quarry  was  but  20  feet 
above  the  base  of  the  dam.  The  time  consumed  in  hoisting  and 
lowering  was  equal  to  one-fifth  of  the  time  taken  to  handle  a  load 
from  the  quarry  to  the  dam. 

249,  Pt  II 


45 

The  cables  were  found  to  be  very  convenient  in  handling  other 
things  needed  besides  rock  in  the  construction  of  the  dam.  Wagon 
roads  were  built  around  the  towers,  and  loads  of  steel  or  lumber  used 
on  the  dam  could  be  taken  directly  from  the  wagons  and  carried  by 
the  cableways  wherever  wanted  to  be  used  or  stored.  A  covering 
of  dirt  sufficient  to  make  a  good  roadbed  was  put  on  top  of  the  dam, 
and  this  now  serves  as  a  roadway  across  the  canyon. 

EAST  CANYON  DAM,  UTAH. 
NECESSITY   FOB,   STRUCTURE   AND   CHOICE   OF   TYPE. 

The  type  represented  by  this  structure  is  a  modification  of  that  of 
the  Lower  Otay  Dam,  just  described.  Considerable  space  is  given 
to  this  enterprise  for  the  reason  that  it  illustrates  what  a  community 
of  fanners  can  accomplish  under  united  action.  It  may  likewise 
serve  to  encourage  other  communities  that  are  short  of  water  to 
join  hands  in  an  effort  to  secure  additional  supplies  by  the  construc- 
tion of  similar  dams.  At  the  time  this  enterprise  was  inaugurated  the 
Davis  &  Weber  Counties  Canal  Co.  owned  a  canal  of  100  cubic  feet 
per  second  capacity,  which  diverted  water  from  Weber  River  10 
miles  southeast  of  Ogden,  Utah.  The  tract  of  land  tributary  to  this 
canal  comprises  about  24,000  acres,  of  which  12,000  is  irrigated. 
This  canal  company,  being  one  of  the  latest  appropriators  of  the 
waters  of  Weber  River,  was  entitled  to  a  portion  of  the  natural  flow 
only  when  there  was  a  surplus.  Usually  about  July  1  of  each  year 
this  company  was  compelled  to  close  its  headgates  and  keep  them 
closed  throughout  the  remainder  of  the  irrigation  period.  Not  being 
able  to  secure  water  after  the  spring  floods  had  subsided,  the  farmers 
under  this  system  could  not  raise  such  crops  as  vegetables  and  small 
fruits,  which  required  water  in  July,  August,  and  September,  but 
were  compelled  to  resort  to  grain  raising  or  to  one  crop  of  hay,  on 
either  of  which  the  profits  were  small.  With  water  for  the  entire 
irrigation  season,  however,  three  crops  of  alfalfa  and  a  large  variety 
of  deciduous  fruits  and  vegetables  could  be  grown  to  perfection. 

To  provide  water  for  irrigation  during  the  latter  part  of  the  sea- 
son, the  company  resolved  to  build  a  storage  reservoir  in  the  Wasatch 
Mountains.  A  suitable  site  was  found  on  East  Canyon  Creek,  a  trib- 
utary of  Weber  River,  and  work  was  begun  in  1897.  This  creek  at 
the  dam  site  has  a  flow  of  about  1,200  cubic  feet  per  second  in  flood 
time,  but  is  reduced  to  about  10  cubic  feet  per  second  in  September. 
In  selecting  the  site,  advantage  was  taken  of  a  narrow  gorge  in  the 
stream  channel  about  600  feet  long.  The  site  of  the  structure  as  first 
located  was  wholly  within  the  box  canyon.  This  would  have  permit- 
ted of  the  steel  core  being  vertical  throughout  its  entire  length  of 
100  feet,  which  was  the  original  plan.  In  order  to  lessen  the  cost  of 

249,  Pt  II 


46 

the  foundation,  however,  the  site  was  moved  upstream.  This  necessi- 
tated the  introduction  of  an  angle  in  the  steel  core  years  later,  when 
the  height  of  the  dam  was  increased.  A  plan,  section,  and  elevation 
of  the  dam  and  reconstructed  portions,  as  well  as  some  details,  are 
shown  in  figure  26.  The  following  description  of  how  the  original 
dam  and  the  subsequent  extensions  were  built  is  taken  from  the  report 
of  the  engineers,  of  whom  Samuel  Fortier,  one  of  the  writers,  was 
consulting  engineer,  and  W.  M.  Bostaph  chief  engineer.  This  report 
was  also  printed  in  an  issue  of  the  Engineering  Record.1 


FIG.  26. — Plan,  elevation,  section,  and  details  of  East  Canyon  Dam,  Utah. 
FOUNDATION  AND  CORE  WALL. 

A  temporary  dam  was  built  about  1,000  feet  above  the  canyon,  and 
the  natural  flow  of  the  creek  was  taken  up,  carried  in  canals  and 
flumes,  and  discharged  into  the  creek  below  the  site.  An  excavation 
15  feet  wide  was  made,  extending  across  the  canyon,  which  at  this 
point  was  54  feet  between  the  side  walls  at  the  ground  level,  and 
solid  bedrock  was  found  at  a  depth  of  35  feet  below  the  surface. 
The  engineers  decided  upon  the  type  of  dam  known  as  "  rock  filled," 
with  a  center  core  wall  of  steel  plate  embedded  in  asphaltum  concrete. 
The  first  step  toward  construction  was  putting  in  a  cement  concrete 
foundation,  which  was  also  a  cut-off  wall.  Bedrock  was  cleared  of  all 
loose  material ;  and  as  it  was  polished  by  the  action  of  water  in  past 
geologic  times,  the  side  walls  and  bottom  were  roughened  by  blasting 
out  several  hundred  cavities  and  filling  the  excavation  with  concrete 
composed  of  1  part  Portland  cement,  2£  parts  clean,  sharp  sand,  and 
5  parts  washed  gravel.  Suitable  sand  and  gravel  were  found  in 


LEngin.  Rec.,  52  (1905),  No.  22,  pp.  594-596. 


249,  Pt  II 


47 

abundance  within  2,000  feet  of  the  dam  site.  This  part  of  the  work 
was  completed  in  March,  1898,  and  in  August  following  a  contract 
was  let  to  build  the  dam.  This  as  originally  built  extended  to  a 
height  of  68  feet  above  the  original  bed  of  the  creek  and  58  feet  above 
the  bottom  of  the  outlet  tunnel.  The  steel-plate  center  wall  was 
composed  of  plates  5  by  20  feet,  riveted  together  with  f-inch  rivets 
on  2^-inch  pitch.  There  were  three  tiers  of  sheets,  the  bottom  tier 
20  feet  in  height  and  f  inch  thick;  the  middle  one  20  feet  in  height 
and  T5ff  inch  thick;  the  top  one  28  feet  in  height  and  £  inch  thick. 
The  seams  were  riveted  and  calked  water-tight,  and  the  whole  was 
covered  with  two  coats  of  refined  asphaltum.  The  foot  of  the  bottom 
tier  was  riveted  between  two  angle  bars  3  by  4|  by  T5F  inch  and 
rested  on  the  concrete  foundation.  The  steel  core  wall  extended 
across  the  canyon  and  1^  feet  into  a  trench  blasted  into  the  side  walls. 
The  steel  center  was  embedded  between  two  walls  of  asphaltum 
concrete,  each  4  inches  thick.  These  walls  were  increased  in  thick- 
ness at  the  ends  of  the  steel-plate  core  wall  to  4  feet  to  make  a  more 
secure  joint  with  the  side  walls  of  the  canyon.  This  concrete  was 
composed  of  30  per  cent  sand  and  TO  per  cent  gravel,  mixed  with 
refined  asphaltum,  allowing  9  pounds  of  asphaltum  per  cubic  foot  of 
mixed  sand  and  gravel.  The  whole  was  mixed  while  heated  to  a  tem- 
perature of  250°  F.  and  deposited  and  rammed  into  place  while  hot. 
The  bottom  of  the  steel  wall  for  a  distance  of  5  feet  up  the  plate  was 
embedded  in  cement  concrete. 

EXCAVATING  AND  PLACING  THE  BOCK. 

A  dry-rock  wall  was  built  up  on  either  side  of  the  core,  the  stones 
being  carefully  laid  and  bonded,  with  all  the  spaces  filled  with 
broken  rock.  Each  wall  was  20  feet  in  thickness  at  the  bottom  and 
10  feet  at  the  top.  The  inner  faces  of  these  walls  were  about  8£ 
inches  apart.  On  the  upstream  side  of  the  dam  a  face  wall  5  feet  in 
thickness  was  laid  on  a  slope  of  1  to  1.  On  the  downstream  side  the 
face  Avail  was  the  same  thickness  and  laid  on  a  slope  of  2  to  1.  The 
portion  of  the  dam  between  these  walls  and  the  walls  next  to  the 
core  was  filled  with  rock  dumped  in,  with  all  the  spaces  carefully 
filled.  The  rock  for  all  this  work  was  procured  by  blasting  it  from 
the  sides  of  the  cliffs  on  either  side  of  the  canyon.  This  fell  in  large 
masses,  many  containing  from  500  to  1,000  cubic  yards  each.  The 
blasting  was  done  before  the  core  was  built  up.  The  rock  that  fell 
on  and  near  the  concrete  foundation  was  removed  and  the  latter 
cleaned  of  all  materials.  The  steel-plate  wall  was  then  set  in  position 
and  the  cement  concrete  around  the  bottom  and  the  asphaltum  con- 
crete deposited  and  rammed.  The  walls  were  built  of  large  stones 
hoisted  into  position  with  derricks. 

249,  Pt  II 


48 

OUTLET  TUNNEL  AND  VALVES. 

The  upper  portal  of  the  outlet  tunnel  is  at  a  point  TO  feet  to  the 
right  of  the  north  end  of  the  dam.  This  tunnel,  originally,  was  190 
feet  long  and  excavated  through  the  solid  rock  side  wall  of  the  canyon 
so  as  to  carry  the  discharge  below  the  downstream  toe  of  the  dam. 
The  tunnel  was  built  horseshoe-shaped,  6  feet  in  height  and  5  feet 
5  inches  in  width.  Two  main  valves  were  located  at  the  upper  portal 
of  the  tunnel,  each  attached  to  a  30-inch  steel  pipe  extending  12  feet 
into  the  tunnel  and  embedded  in  a  bulkhead  of  cement  concrete  which 
securely  closed  the  tunnel  against  the  passage  of  water,  except  through 
the  valves  and  pipes.  Stems,  attached  to  the  valves,  reached  to  an 
operating  platform  attached  to  the  side  of  the  cliff  above  the  surface 
of  the  reservoir.  Two  auxiliary  valves,  in  all  respects  like  the  main 
valves,  were  placed  at  a  point  in  the  tunnel  130  feet  from  the  upper 
portal.  A  shaft  8  feet  square  was  sunk  from  the  cliff  above,  inter- 
secting the  tunnel  at  this  point  and  extending  to  its  floor.  These 
auxiliary  valves  were  the  same  size  as  the  main  valves.  Each  was 
connected  to  two  30-inch  cast-iron  pipes,  which  extended  a  short 
distance  into  the  tunnel  either  way,  and  were  likewise  embedded  in 
solid  bulkheads  of  concrete.  Valve  stems  reached  to  an  operating 
platform  built  on  top  of  the  valve  chamber.  All  the  large  valves 
had  handwheels  at  the  tops  of  the  stems.  To  equalize  the  pressure 
on  both  sides  of  the  main  valves  a  6-inch  pipe  controlled  by  a  sepa- 
rate valve  admitted  water  from  the  reservoir  into  the  upper  portion 
of  the  tunnel.  A  similar  pipe  and  valve  were  used  in  connection  with 
the  auxiliary  gates  to  drain  the  water  from  the  upper  portion  of 
the  tunnel  when  it  was  desired  to  remove  all  pressure  from  the  aux- 
iliary gates.  By  this  means  the  operation  of  either  set  of  gates  was 
facilitated. 

WASTEWAY. 

Since  it  was  intended  to  increase  the  height  of  the  dam  whenever 
means  were  available,  a  temporary  wooden  wasteway  was  built  to 
by-pass  the  flood  flow  of  the  stream  when  the  reservoir  was  full.  A 
wasteway  30  feet  wide  and  6^  feet  deep  is  provided,  being  located 
on  the  south  end  of  the  dam.  A  flume  constructed  of  lumber  resting 
on  a  shelf  built  into  the  side  wall  of  the  canyon  extends  190  feet  on  a 
grade  of  1  in  8  to  a  point  beyond  the  toe  of  the  dam,  and  discharges 
the  surplus  water  over  and  against  a  rock  cliff  below.  (PI.  VIII, 
fig.  1.) 

RESULTS  SECURED. 

The  dam  and  the  rest  of  the  work  were  completed  April  1,  1899. 
Twenty-three  thousand  cubic  yards  of  rock,  810  cubic  yards  of  cement 
concrete,  183  cubic  yards  of  asphaltum  concrete,  69,800  pounds  of 

249,  Pt  II 


49 

steel,  and  50,500  feet,  board  measure,  of  lumber  were  used  in  the  con- 
struction. The  total  cost  was  $50,200.  The  capacity  of  the  reservoir 
was  3.845  acre-feet,  which  gives  a  cost  of  $15.65  per  acre-foot.  The 
area  of  the  surface  of  the  reservoir  at  58  feet  above  the  bottom  of  the 
tunnel  was  225.4  acTes. 

The  water  in  the  reservoir  was  rising  rapidly  at  the  time  of  the 
completion  of  the  dam,  and  within  two  weeks  thereafter  was  dis- 
charging through  the  wasteway.  About  six  weeks  after  this  the 
valves  were  closed  and  the  leakage  was  measured.  This  was  found  to 
be  2.7  cubic  feet  per  second  coming  through  innumerable  small  holes 
through  the  rock  cliffs  on  each  side  of  the  dam.  The  company  began 
drawing  on  the  reservoir  for  its  canal  on  July  5,  1899,  using  a  flow 
of  50  cubic  feet  per  second.  During  the  winter  of  1899-1900  but 
little  snow  fell  in  the  mountains,  and  all  the  streams  became  low  early 
the  following  spring.  The  company  opened  its  reservoir  gates  on 
June  22  and  supplied  its  customers  with  water  for  two  months  at 
a  time  when  other  canals  were  dry. 

BAISING  THE  DAM. 

In  the  summer  of  1900  the  dam  was  examined  with  a  view  to  rais- 
ing it  25  feet  higher.  It  was  found  that  the  dry  walls  had  settled 
about  1  foot,  the  steel  plate  being  in  good  condition.  A  contract  was 
let  for  raising  the  dam  to  83  feet  above  the  outlet  tunnel.  The  plan 
followed  lines  similar  to  those  of  the  original  dam,  except  that  the 
steel  core  wall  was  inclined  downstream  at  an  angle  of  30°  from 
the  vertical,  which  was  necessary  to  connect  properly  with  the  side 
walls  of  the  canyon.  The  rock  was  removed  from  around  the  steel 
to  a  depth  of  10  feet  and  the  new  steel  was  riveted  as  in  the  original 
dam  and  covered  with  hot  asphaltum.  The  walls  on  the  downstream 
side  were  built  up  to  the  full  height  of  25  feet  and  the  steel  core  wall 
was  anchored  to  them.  The  lateness  of  the  season  made  it  necessary 
to  suspend  work,  close  the  valves,  and  begin  to  store  wrater  before 
the  upstream  side  of  the  steel  plate  was  properly  protected.  (PI. 
VIII,  fig.  2.)  The  reservoir  was  used  in  1900  and  1901  without  any 
protection  to  the  steel  plate.  The  cost  of  this  improvement  was 
$35,500. 

The  capacity  of  the  reservoir  was  increased  by  this  addition  to 
8,895  acre-feet,  which  provided  70  cubic  feet  per  second  of  water 
for  60  days.  The  surface  of  the  enlarged  reservoir  became  262  acres. 
In  1901  an  estimate  was  made  of  the  value  of  the  crops  produced 
with  reservoir  water,  and  the  aggregate  was  found  to  be  over  $40,000, 
which  figure  will  be  materially  increased  when  several  hundred  acres 
of  young  orchard,  irrigated  with  water  from  this  reservoir,  come 
into  full  bearing. 

249,  Pt  II 


50 

SECOND   ADDITION. 

In  the  fall  of  1902  the  company  decided  to  add  another  17  feet  to 
the  height  of  the  dam  and  bring  it  up  to  an  even  100  feet  above  the 
outlet  tunnel,  as  originally  contemplated.  An  examination  showed 
that  that  part  of  the  steel  core  wall  that  had  been  left  unprotected 
was  in  such  condition  as  to  necessitate  taking  it  down  and  rebuilding 
it,  and  before  work  was  commenced  the  steel  fell,  carrying  part  of 
the  rear  wall  with  it.  The  rivets  were  cut,  the  plates  removed  and 
rebuilt,  continuing  the  core  at  an  angle  of  45°  from  the  vertical. 
On  the  downstream  side  of  the  steel  core  a  rough,  rubble  masonry 
wall,  6  feet  in  thickness,  laid  in  cement  mortar,  was  built  5  inches 
from  the  steel  core  wall,  and  this  space  filled  with  hot  asphaltum 
concrete  mixed  as  in  the  original  dam,  and  tamped  into  place.  Next 
to  the  steel  plate  on  the  upstream  side  a  layer  of  4  inches  of  asphaltum 
concrete  was  laid.  This  was  covered  with  lumber  4  inches  thick.  A 
facing  of  stone  was  laid  over  this  10  feet  thick.  At  the  ends  of  the 
steel  plate  trenches  were  cut  into  the  rock  and  the  asphaltum  concrete 
widened  out  to  4  feet  on  each  side  next  to  the  side  walls.  The  top 
width  of  the  dam  was  made  15  feet.  The  downstream  slope  remained 
at  2  to  1.  The  form  and  location  of  the  wasteway  wrere  the  same  as 
in  the  original  dam  and  extended  beyond  the  toe  of  the  dam. 

The  main  and  auxiliary  valves  were  examined  and  found  to  be  in 
good  condition.  Additional  gearing  and  stems  were  added  to  bring 
the  handwheels  above  the  top  of  the  dam  and  render  them  more 
easily  operated.  A  lining  of  4  inches  of  cement  concrete  was  put 
into  that  part  of  the  tunnel  above  the  main  valves;  and  the  lower 
end  was  extended  by  cutting  under  the  cliffs  and  discharging  the 
water  beyond  the  toe  of  the  dam  as  enlarged.  The  work  was  not 
completed  until  the  spring  of  1904.  On  May  13  the  reservoir  was 
full  of  water.  There  was  found  to  be  no  perceptible  increase  in 
leakage  through  the  dam,  and  every  part  proved  in  operation  to  be 
all  that  was  anticipated. 

COST  OF  DAM. 

The  entire  cost  of  the  dam  and  reservoir  from  the  date  of  the  first 
surveys  in  1894  until  the  completion  of  the  third  portion  of  the 
structure  in  1904  is  given  in  the  following  itemized  statement.  The 
item  for  sundry  expenses  includes  a  large  number  of  individual  ex- 
penditures such  as  measuring  weirs,  a  building,  repairs,  etc.,  which 
have  been  grouped  under  this  head: 

249,  Pt  II 


51 

Itemised  statement  of  cost  of  East  Canyon  Dam,  Utah. 

Excavation  of  foundation,  940  cubic  yards,  at  $2.30  per 

yard $2, 162 

Portland-cement  concrete,  1,520  cubic  yards,  at  $8.50  per 

yard 12,  920 

Asphaltum  concrete,  660  cubic  yards,  at  $10  per  yard 6,  600 

Steel  plate  in  place,  164,200  pounds,  at  7  cents  per  pound—  11, 494 
Masonry  laid  in  cement  mortar,  2,280  cubic  yards,  at  $6 

per  yard 13,680 

Excavation  of  tunnel  and  valve  chamber,  520  cubic  yards, 

at  $8  per  yard 4,160 

Lumber,  120,000  feet,  at  $30  per  M  feet 3,  600 

Valves,  stems,  pipes,  and  appurtenances 2,400 

Rock  derrick  placed  in  wall,  28,000  cubic  yards,  at  $1.24 

per  yard 34,  720 

Rock  blasted  down  into  dam,  68,600  cubic  yards,  at  25 

cents  per  cubic  yard 17,125 

Land  purchased 1,000 

Roads  and  bridges  around  reservoir- __  1,500 

Sundry  expenses 8,000 

Engineering,  superintendence,  and  incidental  expenditures-  8,000 


Total ._  127,361 

The  available  capacity  of  the  completed  reservoir  at  the  100-foot 
level  from  the  outlet  tunnel  and  at  the  145-foot  level  from  bedrock 
is  13,800  acre-feet  and  its  area  280  acres.  Comparing  the  total  cost 
with  the  available  capacity,  the  cost  per  acre-foot  is  $9.23.  The  term 
"  available  capacity  "  is  here  used  because  in  operation  it  has  been 
found  that  the  computed  capacity  of  the  reservoir  has  been  consid- 
erably increased  by  water  stored  in  underground  reservoirs,  which  as 
the  reservoir  is  drawn  down  returns  to  the  main  reservoir  and  in 
this  way  not  only  compensates  for  the  loss  due  to  evaporation,  but 
provides  about  6  per  cent  in  addition. 

In  1904  a  continuous  stream  of  115  cubic  feet  per  second  was  drawn 
from  the  reservoir  for  62  days.  The  water  flows  through  the  channel 
of  East  Canyon  Creek,  mingling  with  the  natural  flow  to  the  junction 
of  Weber  River,  thence  down  Weber  River  to  the  company's  head- 
gate,  where  it  is  diverted  into  the  canal,  now  enlarged  to  200  cubic 
feet  per  second  capacity. 

BENEFICIAL   EFFECTS   OF   ENTERPRISE. 

From  a  financial  point  of  view  the  enterprise  has  been  more  suc- 
cessful than  the  most  sanguine  of  its  friends  anticipated.  A  careful 
estimate  of  the  crops  produced  by  reservoir  water  in  the  year  1904 
shows  their  value  to  be  over  $75,000,  or  more  than  58  per  cent  of  the 
cost  of  the  entire  storage  works.  Moreover,  the  value  of  the  land 
under  this  canal  has  increased  on  an  average  100  per  cent.  Many 

249,  Pt  II 


52 

hundreds  of  acres  of  orchard  have  been  planted  that  are  beginning  to 
bear  fruit,  all  made  possible  by  the  construction  of  this  reservoir.  A 
water  right  in  this  canal  and  reservoir  is  regarded  as  one  of  the  best 
in  the  State. 

MILNER  DAM,  IDAHO. 

This  dam,  on  the  Snake  River  in  Idaho,  is  a  good  example  of  the 
loose-rock  and  earth-fill  type.  The  data  herein  given  is  taken  largely 
from  Schuyler's  work  on  reservoirs.1  This  structure  consists  of  three 
dams,  closing  the  main  deep  channel  and  two  high-water  channels  of 
the  river.  Figure  27  gives  a  plan  and  section  of  these  dams,  and 


PIG.  27. — Plan  and  section  of  Milner  Dam,  Twin  Falls  project,  Snake  River,  Idaho. 

figure  28  gives  a  general  view  from  the  downstream  side.  The  gen- 
eral plan  of  all  these  dams  was  practically  the  same,  but  in  construct- 
ing the  main-channel  dam  the  work  was  rendered  more  difficult  owing 
to  the  necessity  of  handling  the  low-water  flow  of  the  river.  The 
south  and  middle  dams  were  constructed  first,  and,  being  located  in 
channels  which  were  dry  except  at  periods  of  high  water,  their 
construction  was  comparatively  easy. 

The  building  of  these  two  dams  will  be  first  considered.  The  rock- 
fill  portion  was  constructed  with  slopes  of  1|  to  1  on  the  lower  side 
and  f  to  1  on  the  upper  side.  The  entire  surface  beneath  the  rock 

1  J.  D.  Schuyler.     Reservoirs  for  Irrigation,  Water  Power,  and  Domestic  Water  Supply. 
New  York  and  London,  1908,  2.  ed.,  pp.  68-74,  125-127. 
249,  Pt  II 


53 

fill  was  first  stripped  of  earth  and  loose  material  before  any  rock 
from  the  main  quarries  or  the  canal  excavation  was  dumped-  into 
place.  A  trench  5  feet  deep  and  5  feet  wide  was  then  cut  into  the 
solid  rock,  the  center  line  of  which  was  directly  under  the  center 
line  of  the  crest  of  the  rock-fill  portion  of  the  dam.  This  trench  was 
extended  up  along  the  side  walls  of  the  canyon.  A  concrete  wall 
3  by  3  feet  was  built  in  the  bottom  of  this  trench,  and  a  vertical, 
double-lap,  pine  plank  fence  having  its  bottom  embedded  in  the  con- 
crete reached  to  the  estimated  level  of  the  high-water  mark  of  the 
reservoir  after  completion. 

About  2  feet  of  concrete  was  placed  in  the  trench  before  starting 
to  build  the  wooden  fence,  and  after  the  lower  section  of  the  latter 


FIG.  28. — General  view  of  Milner  Dam,  Snake  River,  Idaho :  A,  Control  or  wastegates  on 
canal ;  B,  Headgates,  North  Side  Canal ;  C,  North  dam,  length  340  feet  on  top  ;  D,  Spill- 
way, concrete  apron  ;  E,  Middle  dam,  length  335  feet  on  top ;  F,  Regulating  gates  (99)  ; 
G,  South  dam,  length  560  feet  on  top.  Total  length  of  structure  2,100  feet. 

was  in  position  the  concrete  was  built  up  another  foot  on  each  side 
of  it.  In  placing  the  fence,  vertical  3  by  6  inch  studding  were 
erected  every  2  feet.  These  studding  were  of  Oregon  fir,  of  irregular 
lengths,  and  were  lapped  2^  feet  in  splicing  the  joints  as  the  fence  was 
built  up.  Planking  2  by  12  inches  by  12  feet,  and  longer,  surfaced  on 
one  side  and  two  edges,  were  closely  spiked  against  these  studding  in 
two  layers,  making  a  total  thickness  of  4  inches.  The  second  layer 
was  so  laid  as  to  break  joints,  in  all  directions,  with  the  first.  Each 
plank  in  the  first  la}Ter  was  nailed  to  each  studding  with  two  or  more 
40-penny  spikes.  The  outer  layer  was  spiked  in  the  same  manner 
with  GO-penny  spikes.  The  fence  was  kept  about  5  feet  higher  than 
the  stonework  on  either  side,  and  great  care  was  taken  to  maintain 
the  horizontal  and  vertical  alignment.  The  rock  for  the  first  5  feet 

249,  Pt  II 


54 

on  each  side  of  the  fence  was  laid  by  hand,  care  being  taken  to  chink 
up  the  holes,  fill  the  voids  as  closely  as  possible,  and  support  the 
fence  and  keep  it  in  line.  The  toe  walls  consisted  of  large  rock,  none 
of  which  was  to  weigh  less  than  1,000  pounds,  and  50  per  cent  of 
which  were  to  weigh  3,000  pounds  and  upward.  These  rocks  were 
swung  into  place  by  derricks,  and  were  so  placed  that  the  outer  slopes 
of  the  toe  walls  were  about  1^  to  1.  The  portion  of  the  embankment 
between  the  toe  walls  and  the  core  wall  was  made  of  rock  taken  from 
the  canals,  clumped  in  loosely  from  cableways,  and  spread  roughly  in 
layers  of  about  2  feet.  The  main  portion  of  the  loose-rock  fill  had  a 
slope  of  f  to  1  on  the  upstream,  and  1|  to  1  on  the  downstream  side. 
Its  upstream  face  was  carefully  laid  by  hand,  making  a  dry  wall  20 


FIG.  29. — Gates  in  Milner  Dam,  Snake  River,  Idaho.     At  times  of  high  water  those  gates  arc- 
raised  to  regulate  flow  in  canals. 

feet  thick  where  it  rested  upon  the  toe  wall,  reducing  to  10  feet  at 
the  top.  Care  was  taken  to  make  level  beds  and  courses  and  fill  all 
voids  with  spawls  of  rock. 

•  Before  building  the  north  or  main-channel  dam  it  was  planned  to 
cut  a  tunnel  through  the  point  of  the  south  island  of  sufficient  size 
to  carry  the  low-water  flow  during  construction.  This  tunnel  con- 
sisted of  eight  sections,  each  5  feet  wide  and  9  feet  high.  The  flow 
of  water  was  controlled  by  heavy  cast-steel  gates,  raised  by  geared 
stands.  (Figs.  29,  30.)  Quoting  from  Schuyler's  work,  already  re- 
ferred to: 

An  earth  embankment  or  cofferdam  was  placed  across  the  channel  approach- 
ing the  head  of  the  tunnel  to  keep  out  water  during  its  construction.     At  the 
same  time  rock  in  large  blocks  was  deposited  in  the  river  channel,  forming 
249,  Pt  II 


55 


two  lines  of  embankment  at  the  upstream  and  downstreflm  toes  of  the  rock 
fill,  leaving  a  space  between  wide  enough  to  permit  the  sinking  of  24  feet  by 
12  feet  timber  cribs,  with  the  upper  faces  on  the  longitudinal  center  of  the 
rock-fill  crest.  The  water  found  its  way  through  and  over  these  parallel 
levees  of  rock,  which  were  built  up  until  the  water  level  was  13  feet  higher 
above  than  below.  By  this  time  the  tunnel  was  completed,  the  cofferdam  was 
blown  up  by  dynamite,  and  as  much  of  the  river  turned  through  the  tunnel 
as  would  go.  About  4,000  second-feet  found  exit  that  way,  and  1,000  second- 
feet  passed  through  the  loose  rock  of  the  channel  dam.  With  the  aid  of  divers 
the  timber  cribs  were  sunk  on  the  center  line  of  the  rock  fill,  and  a  double  thick- 
ness of  sheet  piling  was  spiked  to  the  upper  face  of  the  cribs,  which  were 
loaded  with  stone.  This  piling  was  fitted  to  the  bedrock  bottom  as  carefully 
as  possible,  and  the  joints  made  tight  by  means  of  concrete  in  bags  placed 
against  the  upper  foot- 
ing of  the  sheet  piles. 
This  work  was  done 
in  a  maximum  depth 
of  40  feet  of  water, 
and  finally  all  the 
water  was  forced 
through  the  tunnel. 
The  remainder  of  the 
work  above  the  water 
line  was  similar  in 
plan  to  the  other  two 
dams,  the  wooden 
fence  being  built  as 
a  continuation  of  the 
sheet  piling. 

The  earth  filling 
on  the  upstream 
face  of  these  dams 
was  placed  by  sluic- 
ing the  materials 
through  flumes  to 
the  point  of  dis- 
charge on  the  dam. 
The  material  avail- 
able for  this  pur- 
pose was  a  very 
finely  divided  volcanic  ash,  which  was  found  quite  difficult  to  saturate 
in  bulk.  However,  by  the  use  of  water  pumped  from  the  river,  the 
material,  dumped  into  a  box  at  the  borrow  pit  by  slip-and-wheel 
scrapers  and  dump  wagons,  was  saturated  and  sluiced  through  a 
flume  and  deposited  in  that  form  in  the  embankment.  The  following 
is  a  further  quotation  from  Schuyler: 

The  earth  had  to  be  obtained  at  a  distance  of  2,000  to  8,000  feet  from  the 

dam.     *     *     *     The  volume  of  water  discharged  by  single  4-inch  centrifugal 

pumps  was  about  1.5  second-feet.     The  flumes  were  about  12  inches  square. 

open  at  top.     *     *     *     All  of  the  earth  for  the  south  dam  and  a  large  part  of 

249,  Pt  II 


30. — Milner  Dam,  showing  lifting  apparatus  operated  by 
electric  motor. 


56 

that  for  the  middle  dam,  except  for  the  base,  was  hauled  by  cars  and  electric 
locomotives  from  borrow  pits  a  mile  or  more  away  on  the  south  side  of  the 
river.  It  was  loaded  into  the  cars  either  by  teams  through  traps  or  by  an 
electric  shovel  and  dumped  at  the  nearest  end  of  the  dam  at  such  an  elevation 
that  the  water  would  carry  it  on  a  grade  to  the  further  end.  The  grade  nat- 
urally assumed  by  the  earth  thus  sluiced  was  from  2  to  4  per  cent.  The  liquid 
mud  freely  entered  the  voids  of  the  rock  fill  and  filled  them  solidly  as  far  as 
the  center  core  wall  of  wood.  As  it  rose  in  height  some  slight  leakage  would 
show  below  for  a  time,  but  the  joints  in  the  wood  quickly  swelled  and  filled 
with  mud  and  became  entirely  tight.  The  earth  was  always  20  feet  or  more 
below  the  top  of  the  rock  fill,  and  the  work  progressed  at  such  a  moderate  rate 
that  the  embankments  had  ample  time  to  settle  and  solidify.  The  earth  packed 
so  readily  that  in  four  days'  time  after  sluicing  was  suspended  a  team  could  be 
driven  over  the  embankment  without  sinking  in,  although  while  sluicing  was  in 
progress  a  pole  could  be  pushed  down  into  the  mud  to  a  depth  of  10  feet  or 
more,  particularly  at  the  extreme  end,  where  the  water  stood  longest  in  the 
pool. 

Very  little  surface  drainage  was  required  to  get  rid  of  the  surplus  water.  It 
seemed  to  be  absorbed  and  disappear  without  showing  up  either  above  or  below 
the  dam.  The  earth  came  to  the  dam  in  a  pulverized,  dusty  condition,  and  the 
water  was  sprayed  upon  it  and  at  once  saturated  it  to  the  softest  of  mud. 
About  80  per  cent  of  the  earth  in  the  south  and  middle  dams  was  sluiced  in 
place,  and  20  per  cent  put  in  by  teams  at  the  outer  slope.  The  dry  portion 
constantly  absorbed  moisture  from  the  adjacent  mass  of  mud,  and  thus  became 
equally  hard  and  solid. 

The  hydraulic  filling  of  the  north  or  channel  dam  was  principally  delivered 
from  the  north  side  of  the  river  through  a  flume  into  the  upper  end  of  which 
a  receiving  box  was  placed,  into  which  the  earth  was  dumped  from  wagons 
through  a  trap,  where  the  pumped  water  sluiced  it  down  to  the  dam. 

The  earth  was  loaded  into  the  wagon  by  means  of  a  traveling  excavator  with 
belt  conveyors  that  delivered  a  continuous  stream  of  earth  to  the  wagons  travel- 
ing by  its  side  until  each  received  its  load. 

In  this  case  the  water  used  was  about  1  second-foot,  and  the  lower  end  of 
the  flume  discharged  along  the  upper  side  of  the  wooden  core  wall,  on  top  of 
the  rock  fill,  first  filling  the  voids  in  the  rock  and  then  extending  upstream  into 
deep  water  20  to  30  feet  in  depth.  On  reaching  the  water  it  assumed  a  very 
flat  slope  under  the  water  line  of  6  or  7  to  1.  AVhen  the  fill  had  reached  the 
top  of  the  water  by  this  process  the  slopes  were  drawn  in  to  the  regular  4  to  1 
slope. 

In  the  general  view  of  this  dam  (fig.  28,  p.  53)  already  referred  to, 
the  headgate  of  the  North  Side  Twin  Falls  Canal  is  shown  at  B. 
Similar  headgates  of  the  South  Side  Twin  Falls  Canal  are  shown 
more  in  detail  in  figure  31. 

The  contract  prices  for  this  work  were  as  follows:  Dry  embank 
ment,  27.5  cents  per  cubic  yard ;  earth  embankment,  placed  by  sluicing, 
37.5  cents  per  cubic  yard.     These  prices  were  necessarily  high  on 
account  of  the  remoteness  of  the  locality,  the  high  cost  of  fuel,  labor, 
supplies,  and  materials. 

The  weak  feature  of  this  dam  as  built  is  the  wooden  core  wall. 
The  life  of  the  upper  portion  of  this  wall,  which  is  subject  to  wet  and 

249,  Pt  II 


57 

dry  conditions,  can  not  be  expected  to  be  more  than  10  or  12  years. 
The  designers  evidently  intended  the  wooden  core  wall  as  a  temporary 
expedient  to  insure  water-tightness  until  the  earthen  embankment  in 
front  and  the  material  sluiced  into  the  open  spaces  in  the  rock  had 
been  sufficiently  consolidated  to  insure  imperviousness. 

MINIDOKA  DAM,  IDAHO. 

[TJ.  S.  Reclamation  Service.] 

This  dam  was  constructed  by  the  United  States  Reclamation  Serv- 
ice at  the  head  of  the  Minidoka  Rapids  on  Snake  River  about  6| 
miles  from  Minidoka,  Idaho.  The  work  at  times  was  rendered  very 
dangerous  and  quite  difficult  by  the  high-water  stage  of  the  Snake 
River.  The  flood  flow  of  this  river  June  20,  1906,  near  Minidoka 


FIG.  31. — Headgates,  Twin  Falls  Canal  system,  South  Side,  at  Milner,  Idaho. 

gave  a  total  maximum  discharge  of  24,300  cubic  feet  per  second.  The 
dam  complete  consists  of  a  loose  rock  fill  664  feet  long,  with  a  con- 
crete core  wall  faced  on  the  upstream  side  with  a  heavy  earth  embank- 
ment; a  concrete  spillway,  headgates,  and  forebay  canal.  (Fig.  32.) 
The  length  of  the  entire  structure  is  4,412  feet.  Construction  was 
begun  in  December,  1904,  but  owing  to  various  delays  the  work  did 
not  get  fairly  under  headway  before  January,  1905. 

The  main  dam  is  of  the  loose-rock-fill  type,  with  a  concrete  core 
back  filled  on  the  upstream  slope  with  earth  and  gravel.  This  slope 
has  a  heavy  gravel  face  protected  by  cyclopean  riprap  (fig.  33). 

249,  Pt  II 


58 

Before  constructing  the  loose-rock  fill  a  channel  for  diverting  the 
flow  of  the  river  was  excavated  through  the  rock  point  at  the  north 


FIG.  32.— Minidoka  Dam,  Snake  River,  Idaho  (U.  S.  Reclamation  Service). 

end  of  the  dam.     This  channel  was  closed  by  a  concrete  dam  (fig.  34) 
containing  five  8  by  12  foot  coffin  sluice  gates  (fig.  35).     A  concrete 


240,  Pt  II 


59 

spillway  (fig.  36),  2,385  feet  long,  was  built  at  the  south  end  of  the 
dam,  following  the  highest  ridges  of  rock.     The  excavation  for  the 


FIG.  33. — Uiprapped  slope,  Minidoka  Dam,  Snake  Uiver,  Idaho. 

foundation  of  the  loose-rock  dam  was  practically  all  wet  and  required 
constant  pumping.     Very  little  rock  was  taken  out,  nearly  all  the 


FIG.  34. — Concrete  dam  in  diversion  channel,  Minidoka  project  (U.  S.  Reclamation  Service), 

Idaho. 

material  being  that  which  had  washed  into  the  deep  channel  during 
the  construction  of  the  cofferdam.     This  channel,  though  narrow, 


60 


249,  Pt  II 


61 

was  25  feet  deep,  and  two  rows  of  sheet  piling  had  to  be  driven  full 
depth  ahead  of  the  excavation.  A  break  in  the  cofferdam,  when  the 
excavation  was  practically  complete,  caused  considerable  delay  and 
additional  expense.  Figure  37  shows  the  method  and  sequence  of 
the  construction  of  the  main  loose-rock  dam.  The  portion  in  the 
deep  channel  marked  (1)  wras  constructed  first,  subscripts  showing 
the  sequence  of  construction  in  that  part.  The  water  meanwhile  was 
diverted  through  the  portion  marked  (2) ,  which  was  next  constructed, 
forcing  the  water  back  through  the  diverting  channel.  The  embank- 
ments (1),  (12),  (13),  (2t),  and  (22)  when  finished  formed  a  coffer- 
dam for  the  construction  of  the  core  wall,  after  which  the  upper 


filling  was  continued  across  the  whole  channel.  Practically  all  the 
rock  excavated  from  the  diversion  channel  was  placed  in  the  dam. 
The  average  haul  for  this  portion  of  the  rock,  which  was  a  little  over 
two-thirds  of  the  total  amount,  was  450  feet,  including  haul  by  cable- 
ways.  The  remainder  of  the  rock  was  obtained  from  the  upper  end 
of  the  canal  and  the  haul  averaged  900  feet.  About  one-eighth  of 
the  rock  could  be  reached  directly  by  the  cableway  and  required  no 
hauling  on  cars.  The  cars  used  were  simply  trucks  on  which  the 
skips  were  hauled  from  the  derrick  to  the  cableway,  one  horse  being 
used  to  haul  three  cars.  Two  cableways  were  constructed,  each  1,300 
feet  long  and  consisting  of  a  patent  lock  wire  2  inches  in  diameter. 

249,  Pt  II 


62 

Each  cable  was  supported  by  two  movable  wooden  towers,  81  feet 
high.  These  towers  were  mounted  on  trucks  to  facilitate  their  being 
moved  to  any  line  parallel  to  the  axis  of  the  dam.  The  span  of  the 
cableway  between  the  towers  was  1,150  feet.  The  necessary  carriages 
and  hauling  and  hoisting  lines  for  the  lifting  and  conveying  of  the 
material  were  supported  from  these  cables.  The  hoisting  lines  were 


PROFILE  or  CQpEWAiL. 


U  .  T  .  ?T-T  .  T  .  T* 


SECTION  OH  LIME  C-0. 


FIG.  37. — Plan  and  sections  of  Minidoka  Dam,  Idaho,   showing  sequence  of  construction 
(TJ.  S.  Reclamation  Service). 

operated  by  two  65-horsepower  triple-friction  drum,  reversible,  link- 
motion  hoisting  engines.  Steam  was  supplied  by  two  80-horsepower 
boilers,  one  boiler  and  engine  being  located  on  the  base  of  each  head 
tower.  The  arrangement  of  the  machinery  was  such  that  the  load 
could  be  dumped  at  any  point  by  the  engineman,  the  safe  working 
load  being  7  tons.  The  rock  was  carried  in  heavy  steel  skips,  each 
having  a  capacity  of  3  cubic  yards.  This  method  of  placing  rock 

249,  Pt  II 


63 

while  fairly  economical,  was  open  to  some  objections,  chief  of  which 
was  its  limited  capacity.  When  taking  rock  from  the  canal  it  required 
five  minutes  for  a  skip,  running  at  full  speed,  to  make  the  trip  to 
the  center  of  the  dam  and  back.  This  gave  a  maximum  capacity  of 
120  trips  per  10-hour  day.  The  average  number  was  only  100  trips, 
which,  at  1|  cubic  yards  per  skip  (measured  in  excavation),  gives 
150  cubic  yards  per  day  as  the  average  capacity  of  each  cablewTay. 
The  rock  was  dropped  from  a  height  of  10  to  50  feet  and  made  a 
very  compact  fill.  While  putting  in  the  base  of  the  dam  both  cable- 
ways  were  used,  but  as  the  section  became  narrower  only  one  cable- 
way  could  be  used.  When  the  rock  was  within  15  feet  of  the  top  it 


FIG.  38. — Showing  derrick  handling  skips,  and  cableways  in  action ;  also  showing  double 
trestle  from  which  earth  was  dumped  in  the  back-filling,  Minidoka  project,  Idaho  (TJ.  S. 
Reclamation  Service). 

became  necessary  to  raise  the  embankment  rapidly  on  account  of 
high  water.  For  this  purpose  the  capacity  of  the  cableway  was  in- 
sufficient to  keep  ahead  of  the  water.  It  was  fully  expected  that  the 
river  would  discharge  over  the  spillway  during  the  high  water,  but 
it  rose  only  to  within  3.2  feet  of  the  crest  of  the  weir.  Before  this 
stage  was  reached  the  rock  fill  had  been  raised  to  its  maximum 
height— 52  feet — which  is  13.2  feet  above  the  highest  level  reached 
by  the  river.  At  this  level  the  water  passed  freely  through  the  rock 
fill,  the  leakage  being  estimated  at  1,000  cubic  feet  per  second,  which 
was  evenly  discharged  throughout  the  length  of  the  dam. 

For  the  purpose  of  placing  the  earth-gravel  back  filling  in  the 
dam  a  double  trestle  (fig.  38)  was  built  across  the  river  and  tracks 

249,  Ft  II 


64 

laid  to  the  borrow  pits,  1,200  to  1,800  feet  from  the  nearest  point  on 
the  dam.  An  orange-peel  excavator  with  a  1-yard  dipper  was  in- 
stalled for  loading  the  cars  at  the  borrow  pit.  The  excavator  was 
supplemented  by  hand  shoveling  and  by  traps  and  teams  in  loading 
the  cars.  These  cars  were  of  the  side-dump  type  and  had  a  capacit}7 
of  3  yards,  one  team  of  horses  hauling  three  cars.  A  steam  hoist 
was  used  for  pulling  the  loaded  cars  up  a  slight  incline  to  the  ap- 
proach of  the  bridge  and  for  pulling  empties  off  the  bridge.  The 
elevation  of  the  bridge  was  about  20  feet  below  the  top  of  the  dam. 
When  it  could  be  used  no  longer,  a  track  was  laid  on  top  of  the  rock 
fill  and  the  gravel  and  earth  were  dumped  from  the  cars  into  the 
water.  At  first  a  comparatively  large  percentage  of  this  material 
was  carried  into  the  rock  fill,  but  the  voids  were  soon  filled  and  the 
water  completely  shut  off.  The  entire  loose-rock  fill  was  made  water- 
tight under  those  conditions  and  very  little  settlement  resulted.  This 
latter  condition  is  due  to  the  fact  that  earth  deposited  under  water  is 
formed  into  a  most  compact  embankment,  which  in  most  cases  is 
impervious  to  the  passage  of  water. 


ADDITIONAL  COPIES  of  this  publication 
•cV  may  be  procured  from  the  SUPERINTEND- 
ENT OF  DOCUMENTS,  Government  Printing 
Office,  Washington,  D.  C.,  at  15  cents  per  copy 


University  of  California 

SOUTHERN  REGIONAL  LIBRARY  FACILITY 

405  Hilgard  Avenue,  Los  Angeles,  CA  90024-1388 

Return  this  material  to  the  library 

from  which  it  was  borrowed. 


'••>  Rtc 

QL    OCT17 


OCT  141994 
EMS  LIBRARY 
JAN  2  3  1995 

e  e  «•  i  v  E 

DEC  011994 


THE 
UNIVERSITY  OF  CALIFORNIA 


LITHOMOUNT 

PAMPHLET  BINDER 


6AYLORDWOS.U«.i 


TC 
540 
F77s 
v.2 


Library 


UC  SOUTHERN  REGIONAL  LIBRARY  FACILITY 


A     000213915     2 


University 
Southeri 
Library 


